deleted emails returning in yahoo after the move. cannot delete old emails or old folders after migration

I migrated to yahoo last week with all 4 of my comcast email addresses.  emails and folders i delete in yahoo are returning.  to be clear only emails that migrated from comcast to yahoo are repopulating.  emails and folders received or created since the migration are staying deleted.  only the stuff that migrated over keeps returning after deleting them.  (i tried to be sneaky and move them to archive but they still come back to the original inbox or folder and i end up with multiple copies of stuff im trying to delete!)  also i had a fairly large folder of old emails from 2014 to 2020 and i cant delete any of them or the folder.  On yahoo site it said that the folder could not be deleted until the emails were deleted.. so i deleted around 12,000 emails and the folder was empty.  deleted the folder and a day later the folder and all the emails came back.   

trouble shooting steps i tried.... I disconnected my email accounts from IOS (iphone mail app) and i disconnected my email accounts from Outlook (both the ipnone app and also the desktop app)  then i deleted the yahoo app from my phone.  I went to the yahoo account settings page for each email and i closed all open sessions in my web browsers and also they had an option to disconnect access from IOS and also Outlook so there was no third party access.  everything was disconnected.  all my browsers cache and cookies and data were deleted (chrome, Edge, Safari)  I also followed suggestions to disable conversation view in email apps and also tried changing my password and logging in again.   I was ONLY connected to my new yahoo account on the website and I deleted the emails and folders again.  an hour later they started coming back.  eventually overnight the folders were filling up with returning email.  I cant figure out where they are coming from.  they cant be syncing with other apps because they are all now disconnected and it cant be a sync issue between phone and web because the yahoo phone app was also deleted and data erased.  Because it is only happening to email and folders that were migrated from comcast to yahoo is it resyncing with comcast after i delete it?  Is there something in the data that is migrated that is not allowing it to be removed from the yahoo server or is it still connecting to comcast servers a few days after i moved and repopulating the emails and folders? 

Have you tried logging in here: https://connect.xfinity.com/appsuite

Having the same issue. No migration but deleted and spam emails just reload. 

Update:   a week after the migration all of a sudden the problem went away.  I still don't know why it was happening or what the solution was that corrected it. 

I continued to delete old emails and folders every day, multiple times a day and every time they kept coming back.  (but only the emails and folders that were on my account from before the migration.. the info that migrated over.  as i mentioned all the new emails i was getting after the migration were deleting normally)  

When 5 full days had passed since the day i migrated, suddenly all the stuff was working properly.  I was able to delete old emails and folders and they are staying deleted. 

I am just guessing that it was a sync issue with outlook even though i had disconnected it.  Maybe they were still syncing?

or maybe it was even a server issue on the yahoo side.. Someone online suggested that yahoo may use multiple servers and maybe a "bad" server that was resyncing my old data?? 

I don't know, that is just what someone suggested.  But i do know that now its working properly.  

so i suppose the solution is just patience.. i just needed to wait a week and everything worked itself out.