Take a look at that suggestion - Pool connecting - #3 by Jacek.
If you still have that old SD, maybe somehow you can recover the old config.yaml.
Also, chia logs are rather abusive, so you should also symlink those to that external SSD. Most likely those logs killed your SD, as otherwise there is not much activity there.
I would also suggest that you get @Chris22 involved to get it resolved (if what was suggested already will not help). The errors you listed are most likely coming from Flexpool (chia is just repeating them, not really interpreting). It may be that there is a bug in either chia’s or Flex’s implementation, and it manifests itself with problems with leaving Flex pool (the only one that was reported having such problems, thus suggesting this is Flex’s problem). So, your local installation will suggest that you have already left Flex, but somehow Flex will still cling to your .25 XCH wins, and based on previous report, Flex is not going to return it to you, even if you would be already pooling with a different pool.