We'd be more likely to respond if you weren't using "one throwaway account", and instead used a linked account.
I stopped doing this, because it improves transfer a couple of times and then it can totally choke a transfer and I have to kill Dopus.
Best workaround so far is to use Windows Explorer for large files welp
Yea, I'm just using explorer for transfers and Opus for viewing/searching for files. Hoping for a fix in the future but I see forum issues talking about this from years ago. I'm sure it's not trivial. Explorer now has tabs (insider program), which are helping with more complicated transfers. However, I'd rather stay in Opus of course.