LR 5.7.1 blinks when launched.

Hi,
After updating to Ventura 13.3.1 my Lightroom 5.7.1 acts oddly at start-up - the program blinks (and ball spinning) for about 1 minute, after this period I can navigate within the library module, but if I go over to the develop module the same blinking starts again (same if I go to printing). After this blinking period I can switch between the modules without problems.
On a second volume of the same Mac (silicon), using Ventura 13.2, I have no problem at all using the program.
I have reinstalled the program, starting up a new catalogue, restarting the preferences - nothing helps.
Can any one help? (Of course - this is what to expect of an unsupported outdated program.)
Thanks
/Anders