Exporting creates M4V file and separate audio file - both cannot be opened

[Jennie5FE2]

Ok, start off by saying I am new so apologise if this has been answered already. I have searched for similar questions butcouldn't find the answer. 

Am using a Windows PC (if thats relevant?) 

When exporting am using settings H.264, export video and audio selected, youtube 1080 selected. 

Exports now sometimes hang or when they do complete, places an m4v file and separate audio file in the chosen location - both files cannot be opened. 

Did try to upload the m4v to Youtube but had no sound and it cut off the last 4 mins of the video. 

Have uploaded 5/6 videos without issue before but since yesterday (07/06/21) all these issues are cropping up. 

Thank you for your time

[Ann Bens]

Post screenshot export settings.

[Jennie5FE2]

[Jennie5FE2]

Just uploaded - thanks

[Ann Bens]

Turn off hardware encoding and try again.

[Jennie5FE2]

Just trying that and will let you know - Thanks

[Jennie5FE2]

Ok so tried that and have found that at 78% it freezes and Premier Pro then closes. So Im thinking the 78% is just dumped hence why its showing at an m4v file as I believ it converts to an mp4 file at the end of the export? 

Question is - why is it freezing and crashing at 78% export?

(Thank you for you help so far, very much appreciated)

[Jennie5FE2]

OK so all sorted - seems the crashing at 78% was due to a dodgy section of video. Tested with a render in and out either side of the suspected offending piece and that errored out. Removed it and reinserted and worked a treat. Thank you again for all your help @Ann Bens 

[Jennie5FE2]