Thanks for your reply, Spliff !!
Very cool ideas!
I don't have much time researching the issue right now, but it is on my 2do list.
I changed PC, Win10 version and upgraded UR so these all could be to blame. Frankly, downgrading to previous UR version is the first thing I am going to try. I did the reset etc. described in the UR help. It did not help.
I created two new databases w/o transferring any data into them and the freezing bug still occurred.
I will definitely keep the information you posted about SQLite in my UR notes so that when I need it, I have it handy. I did some minor SQLite editing in the past and could not find a good editor. Perhaps the one that you have suggested could be the way to go for me. I don't need to do this often though.
Best regards
K