If subcribe to folders is changed, they come back for 5 min and disappear

I have an Outlook account linked to Thunderbird, as well as two Gmail accounts and a Hotmail account. All of my accounts are IMAP accounts. Until yesterday, I have had no problems with Thunderbird. Yesterday the sent folder and the subfolders for the Outlook account disappeared. Today the same thing happened to my Hotmail account. I have followed advice such as subscribe to folders, and I unclicked the "show only subscribed folders" in the Advanced Server Setting. The curious thing is that by doing any of the actions mentioned above, the folders will show up only to disappear again minutes later. I have not done any major Thunderbird updates, nor any other computer work, so this is totally puzzling me.