Catalina Mail (13.4) problems

I am having trouble with my wife's mail on both an old iMac and on her newer MacBook Pro (2019). On the same computers my mail account from my user works flawlessly, and it is using exactly the same email client settings. We are using IMAP connecting to a Dreamhost account. The symptoms of the problem are that her email account seems to download new mail just fine, but when you go through emails it does not successfully mark things as read and you are unable to delete emails (clicking the delete button or selecting an email and then clicing on the garbage can icon does nothing generally). Another major symptom is that occassionally the cpu usage for Mail goes up crazy high (like +400%) for periods of minutes. While it is in that state it doesn't necessarily show anything happening under the activity viewer (sometimes it does but sometimes it shows nothing happening). Also, it will all of a sudden decide to start downloading huge numbers of messages (it currently claims to be downloading 19,765 even though nothing has changed). Typically it seems that if I let it finish downloading the massive number of mesages it will then work fine in terms of deleting things and marking them as read until I quit Mail and then restart it - if I do that I seem to be back to the same problem. I tried completely deleting the files in the V7 folder under Library/Mail in order to force it to completely rebuild the account from the server. That did not solve the problem. Is there some other plist file or other file that might be corrupted and explain this behavior? I can't tell if this is a problem on the Macs (seems unlikely since it is on two machines) or a Dreamhost server type problem. Does anybody have recommendations on what I should try next?