MediaRecorder on Chrome produces a truncated mp4 with the ‘avc1’ mediaType

When using MediaRecorder on Chrome (Javascript on windows) with the avc1 option on chrome the generated blob is truncated as opposed to the vp9 option,

Here are the 2 options as explained in Recording video from webcam in MP4 format with MediaRecorder,

//const recorder = new MediaRecorder(stream, { mimeType: "video/mp4;codecs=avc1,mp4a.40.2" });
//const recorder = new MediaRecorder(stream, { mimeType: "video/mp4;codecs=vp9,opus" }

When using

var blob=new Blob(cF.chunks,typeOption);

This one is truncated:

Blob {size: 581270, type: 'video/mp4;codecs=avc1,mp4a.40.2'}

This one is fine:

Blob {size: 1028223, type: 'video/mp4;codecs=vp9,opus'}

Any idea why the file is truncated in the first option?