Hi again, Fuzzy!
Mem's guys tell me they're experiencing troubles importing things from Obsidian because it's a feature they're still testing and iterating on. It should improve in the next months to come.
Meanwhile, they bet on exporting the Obsidian Vault as markdown and using their markdown/Plaintext import, which is their most reliable import method at the moment.
I think it's pretty straightforward because all the files in Obsidian are markdown files.
They've also told me trying to import in small batches in case it doesn't work properly.
Hope it helps!
Cheers!