This seems to be broken with my Pixel XL. Directory Opus 12.17, Android 10.
When I transfer files with explorer it works. When I transfer with Opus it hangs after about 100k of data is transferred. I tried both mtp_enable on and off.
Nothing changed on our side.
With Android, using FTP is a lot easier and more reliable than trying to get MTP to function properly.
FTP is extremely slow though, that's the problem.
Well, I may have found a solution. You can use ADB to direct TCP ports over the USB connection, so it charges and works at much higher speed than wifi.
It's still slow because FTP is slow e.g. with many files, but it's slightly better.
Edit: I should mention that I only recently upgraded to Opus 12. Why doesn't it work when Explorer does?