There's too much happening at the same time. MongoDB may not be ready to handle all of it.
You added a fresh node while one was recovering.
The arbiter is not a concern until you need an election and 3 out of 4 possible votes. I say remove it after everything is OK or if you find yourself in a situation where you don't reach a majority of votes.
Good luck with your recovery!
Regards,
Luciano
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