Update here:
I switched back my nameservers to the domain host (GoDaddy - ugh) and used the external dns settings to match the DNS generated by MiaB. This brought my mail back online, but doesn’t fix the issue.
I am thinking of letting this propagate for a week and then try setting it back to my MiaB nameserver so that I can see if that was enough of a refresh. Any thoughts from anyone on this process or any pitfalls/gotchas I should be aware of?