Each time we've done a transfer there's been some amount of manual tinkering to get everything up and going.
For example the problem with @hotmail accounts has been around for years but not a problem until we needed people to actually receive emails.
And Vanilla didn't allow spaces in usernames for new signups but they were imported with spaces. So this forum is more strict on that but we could've fixed it awhile ago.
But this version of this forum I reckon is the most stable it's been since OG Blitz. Every other version has felt like a hack job behind the scenes.