Hi, did you check this, this and this? I got the similar errors when trying to run the indexing but after a few retry it works.
I tried to index email mailbox separately (by running the command inside the rebuild-index.sh for each mailbox separately) and identified which one caused the problem, then I had to open/read the problematic folders with a mail client, and then the index worked.
Given this feels like another duplicate, @staff, there might be something up / to improve with how the indexing is handled.