Outlook IMAP slow folder sync

Outlook IMAP slow folder sync

Hi!
Since 26.09 we experience following problem: new emails syncs into folders with delay. Before 26th of September mails appeared instantly in inbox, now it takes from 30 minutes to infinity.
I see new mails in webmail but none in Outlook.

Closing and reopening Outlook OR moving between folders helps force sync mails.
No settings were changed.
This problem exists on Outlook 2010/2013/2016.

I tried repairing mail account and this helped for a few minutes.