VP Vers. 8.90 & 10.79
I have found many EXPORT issues are solved by rebooting after editing, then reopen and export first thing.
I will generally produce multiple sequences in edit then reboot to export.
Time consuming but seems to be effective in solving export video which stops playing but the position and or sound continues as well as some black screen issues.
Most recently pan and zoom on clips would move video across the screen in export mp4. Rebooted and exported again worked for that as well.
JKL