It's probably not Opus itself as much as MTP in general is a broken mess at both ends (Windows and most phones). It can get in a state where it stops responding in some or all processes, for example, and it really doesn't like more than one process or thread accessing it at the same time.
There are some changes in Opus 13 which improve things a bit by limiting how many MTP requests we make in parallel, but I doubt MTP will ever be that reliable, in Opus or File Explorer or anything really.
I try to avoid MTP entirely and instead use FTP or SMB. MTP and transferring files with Android and iOS phones, Cameras lists some alternatives. I used to run an SFTP server on my Android phone but after switching to iOS I found a phone-side file manager with really good SMB support and copy things to/from the phone using that, over wifi. (There are some FTP servers for iOS as well but I haven't tried them myself.)