See this closed link for a description.
https://community.quicken.com/discussion/7912466/slow-transition-between-accounts-screen-snaps-in-and-out-of-focus I still have this problem. It starts after a transaction download when I have two or more accounts with pending transactions. The last update, R40.21 - 21.1.40.21 did not correct it, in fact it seems worse.