POP mails stopped being imported from my hotmail since some time. I noticed it recently but could not make it work again. Switching to the new (to me, anyway) "gamilify" option from within Gmail settings - I experienced a similar avalanche. Probably two-three weeks ago, but these emails were from decades ago until recent. They did not go to junk, but they were labelled as "email/x/x/junk".
I haven't been able to access my gmail in years -- iOS apparently doesn't back up TOTP generators when you back up your iphone, and the so called "recovery codes" did not work. (I even went into an encrypted volume to check I hadn't made a transcription error since I had transcribed the codes for several sites into a notebook I kept ina safe)
No other service has failed in this way. (A few others, I used recovery codes to regain access with zero issue)
Since I had ported my childhood cell # into google voice, I couldn't access SMS MFA, and thus was locked out.
It's no surprise you're having an odd bug, but at least you have access to your email -- I'd encourage you to export it ASAP and move to a provider who can manage their infrastructure properly.