I can feel your pain mate. So sorry to hear about your problems. I think I’ve seen everything except the network path not found error several times. And I’ve whined about the similar unfortunate problems as you’re experiencing.
There are several threads how to fix the non-empty blocksets problem. Yet I think personally I never did that, because there wasn’t any easy and simple way to get it done. In my case, luckily the backup sets were so small that it was trivial for me to just store the old backup for a few months and start the primary backup from fresh. But for some of my backups in terabyte range, I really were hoping to be able to get the state restored without full re-upload.
Also if you’re not using latest version of Duplicati, do update. Because these problems used to occur lot more often previously than with newer versions.
I hope you’ll get that fixed, but if you’re in hurry, just stash the old backups for a while and restart fresh, much faster and lot less pain to go through.