Are you sure about the re-uploading part? I've had an issue like that last week, and am currently stuck with my mails locally, not able to 'put them back' to the IMAP server. Not Gmail though.
I most definitely did re-upload it without any issues to another G suite account. It was in 2014 though, maybe something did change since then. Here [1] people write that there are probably some differences between Gsuite and regular gmail accounts.
Andrew_nenakhov|4 years ago
[1]: https://superuser.com/questions/446135/import-e-mail-via-ima...
vetinari|4 years ago