diff --git a/DeepDrftContent.Services/Audio/WavOffsetService.cs b/DeepDrftContent.Services/Audio/WavOffsetService.cs
index c5467c3..e40a59b 100644
--- a/DeepDrftContent.Services/Audio/WavOffsetService.cs
+++ b/DeepDrftContent.Services/Audio/WavOffsetService.cs
@@ -112,8 +112,11 @@ public class WavOffsetService
             if (chunkSize < 0)
                 return null;
 
-            if (chunkId == "fmt ")
+            if (chunkId == "fmt " && !foundFmt)
             {
+                // Use the first fmt chunk encountered — that is the WAV-spec-authoritative
+                // chunk. Subsequent fmt chunks in a malformed file are ignored, matching
+                // AudioProcessor.FindChunk which also returns the first match.
                 if (chunkSize < 16)
                     return null;
 
diff --git a/DeepDrftContent/Controllers/TrackController.cs b/DeepDrftContent/Controllers/TrackController.cs
index ee9b3b1..da65828 100644
--- a/DeepDrftContent/Controllers/TrackController.cs
+++ b/DeepDrftContent/Controllers/TrackController.cs
@@ -125,6 +125,16 @@ public class TrackController : ControllerBase
     public async Task<ActionResult> PutTrack(string trackId, [FromBody] AudioBinaryDto track)
     {
         _logger.LogInformation("PutTrack called with trackId: {TrackId}", trackId);
+
+        // Reject unknown MIME types up front rather than silently storing the binary
+        // with a ".bin" extension. GetExtension returns ".bin" for any unrecognised
+        // MIME, so treat that as the sentinel for an unsupported type.
+        if (MimeTypeExtensions.GetExtension(track.Mime) == ".bin")
+        {
+            _logger.LogWarning("PutTrack rejected: unsupported MIME type '{Mime}' for track {TrackId}", track.Mime, trackId);
+            return BadRequest($"Unsupported MIME type: {track.Mime}");
+        }
+
         var audioBinary = AudioBinary.From(track);
         // Direct FileDatabase write: this endpoint receives an already-processed AudioBinaryDto,
         // not a WAV file, so TrackService.AddTrackFromWavAsync does not apply. See constructor comment.
diff --git a/DeepDrftWeb.Client/Services/StreamingErrorHandler.cs b/DeepDrftWeb.Client/Services/StreamingErrorHandler.cs
index 84ba02a..a84e862 100644
--- a/DeepDrftWeb.Client/Services/StreamingErrorHandler.cs
+++ b/DeepDrftWeb.Client/Services/StreamingErrorHandler.cs
@@ -10,15 +10,18 @@ public static class StreamingErrorHandler
         
         return lowerError switch
         {
-            _ when lowerError.Contains("network") || lowerError.Contains("connection") || lowerError.Contains("timeout") => 
+            _ when lowerError.Contains("network") || lowerError.Contains("connection") || lowerError.Contains("timeout") =>
                 "Unable to load audio. Please check your connection and try again.",
-            
-            _ when lowerError.Contains("audio") || lowerError.Contains("decode") || lowerError.Contains("format") => 
+
+            _ when lowerError.Contains("header") || lowerError.Contains("wav") || lowerError.Contains("invalid wav") =>
+                "This file format is not supported. Only WAV files can be played.",
+
+            _ when lowerError.Contains("audio") || lowerError.Contains("decode") || lowerError.Contains("format") =>
                 "This audio file may be corrupted or in an unsupported format.",
-            
-            _ when lowerError.Contains("cancel") || lowerError.Contains("abort") => 
+
+            _ when lowerError.Contains("cancel") || lowerError.Contains("abort") =>
                 "Audio loading was cancelled.",
-            
+
             _ => "Unable to play audio. Please try again."
         };
     }
diff --git a/DeepDrftWeb/Interop/audio/PlaybackScheduler.ts b/DeepDrftWeb/Interop/audio/PlaybackScheduler.ts
index c4ff178..577b83d 100644
--- a/DeepDrftWeb/Interop/audio/PlaybackScheduler.ts
+++ b/DeepDrftWeb/Interop/audio/PlaybackScheduler.ts
@@ -64,7 +64,10 @@ export class PlaybackScheduler {
      * Get current playback position in seconds (includes playbackOffset for seek-beyond-buffer)
      */
     getCurrentPosition(): number {
-        if (this.playbackAnchorTime === 0) {
+        // Use isActive_ as the sentinel for "playback is running", not playbackAnchorTime == 0.
+        // AudioContext.currentTime can legitimately be 0 at context creation, so comparing
+        // against 0 would incorrectly treat an active stream started at t=0 as paused.
+        if (!this.isActive_) {
             return this.playbackAnchorPosition + this.playbackOffset;
         }
         const elapsed = this.contextManager.currentTime - this.playbackAnchorTime;
@@ -143,8 +146,11 @@ export class PlaybackScheduler {
             return; // No new buffers
         }
 
-        if (this.nextScheduleTime === 0) {
-            this.nextScheduleTime = this.contextManager.currentTime + 0.01;
+        // Use isActive_ as the sentinel for "playback is running", not nextScheduleTime === 0.
+        // AudioContext.currentTime can legitimately be 0 at context creation, which would cause
+        // nextScheduleTime === 0 to incorrectly reset a value already set by playFromPosition.
+        if (!this.isActive_) {
+            return;
         }
 
         this.scheduleBuffersFrom(this.nextBufferIndex, 0);
diff --git a/DeepDrftWeb/Interop/audio/StreamDecoder.ts b/DeepDrftWeb/Interop/audio/StreamDecoder.ts
index 3162ba6..f8d4783 100644
--- a/DeepDrftWeb/Interop/audio/StreamDecoder.ts
+++ b/DeepDrftWeb/Interop/audio/StreamDecoder.ts
@@ -51,6 +51,9 @@ export class StreamDecoder {
     private contextManager: AudioContextManager;
     private wavHeader: WavHeader | null = null;
     private rawChunks: Uint8Array[] = [];
+    // totalRawBytes and processedBytes are JS number (IEEE 754 double), which can
+    // represent integers exactly up to 2^53 bytes (~8 PB). WAV files are bounded
+    // at 4 GB by the 32-bit RIFF size field, so overflow is not a practical concern.
     private totalRawBytes: number = 0;
     private processedBytes: number = 0;
     private totalStreamLength: number = 0;
diff --git a/DeepDrftWeb/Interop/wavutils.ts b/DeepDrftWeb/Interop/wavutils.ts
index 0ef0390..b60fd13 100644
--- a/DeepDrftWeb/Interop/wavutils.ts
+++ b/DeepDrftWeb/Interop/wavutils.ts
@@ -22,11 +22,16 @@ class WavUtils {
         // Need a DataView that spans the entire buffer for chunk searching
         const view = new DataView(concatenated.buffer);
 
+        // Allocate TextDecoder once for the entire parse pass. Constructing it
+        // inside the chunk-walk loop would create a new instance per iteration,
+        // which is non-trivial and unnecessary — a single instance is reusable.
+        const decoder = new TextDecoder();
+
         // Check RIFF header
-        const riff = new TextDecoder().decode(concatenated.slice(0, 4));
+        const riff = decoder.decode(concatenated.slice(0, 4));
         if (riff !== 'RIFF') return null;
 
-        const wave = new TextDecoder().decode(concatenated.slice(8, 12));
+        const wave = decoder.decode(concatenated.slice(8, 12));
         if (wave !== 'WAVE') return null;
 
         // Variables to store parsed header info
@@ -43,7 +48,7 @@ class WavUtils {
         // Find fmt and data chunks
         let chunkOffset = 12;
         while (chunkOffset < totalSize - 8) {
-            const chunkId = new TextDecoder().decode(concatenated.slice(chunkOffset, chunkOffset + 4));
+            const chunkId = decoder.decode(concatenated.slice(chunkOffset, chunkOffset + 4));
             const chunkSize = view.getUint32(chunkOffset + 4, true);
 
             if (chunkId === 'fmt ') {