why copying big file fails?

[a <loushanguan2015@sina.com>]

i create video mp4 with android's screen-recorder, it's about 4G

i connect it to debian with jmtpfs and copy it to ext4 hard disk with 
more than 10G  of free space

it fails: cp: error reading 
'DCIM/ScreenRecorder/Screenrecorder-2022-01-30-12-29-58-111.mp4': 
Invalid argument

i run "ls -l", about 2G has been copied

i've play this mp4 using android, didn't meet reading error

BTW which package in bullseye can play mp4? mplayer has failed, and some 
player require gnome , but i haven't installed gnome