What does your Opus config look like?
I would try turning off any columns that cause file contents to be read (image dimensions, Description column, etc.)
It may also be worth turning off Preferences / Folder Tree / Contents: Zip files and other archives in case an archive on the MTP device is being scanned by the tree. (I'm not sure if the setting affects MTP devices, but it's worth a quick test.)
After making the changes, fully exit Opus and then restart it to see if they help. It seems like something is tying up the device, so that will eliminate some of the possibilities at least.