I own an IT company that specializes in QB Enterprise. Most clients are on V20. One of my largest with 30 users, had one user report this happening about 2 weeks ago from today 05/25/21. We ran the Tool Hub, and during the CMD screen it reported that it was unable to find the path to reboot.bat and the issue was not fixed. 

Today, another user at the same company reported the same issue had just started with her. Not all users are experiencing this, so I don't believe it's data corruption of the QB files. This started with a Microsoft Update and a QB update occurring at almost the same time. 

One thing I found is that if you use the webmail, the template text retains it's modified text. Therefore, I believe this is an issue between QB and MS Outlook. The two users are on different versions of Outlook. 

I am also on Enterprise V20, with Outlook 365. This is not happening with the interaction between QB and Outlook, but this needs to get fixed for the people this is happening too. 

The ability to add notes or change the email template on the FLY is very important. I also write personal notes about estimates and invoices so I understand the frustration of my clients this is happening to. Since Intuit "Values my Feedback", I'm going to give them a piece of my mind for blowing this off.