The update seems correct now. To avoid connection problems, I downloaded the 3.15 flash file and updated it offline with Update. I did a factory reset and restored the backup created with HX Edit 3.15
When everything seemed correct, I plugged in my guitar, but couldn't switch memories and couldn't get the buttons to work. After rebooting several times, everything seems to be fine now. I'm guessing there were still internal update processes running that weren't visible on the LT's screen...or that's what I'd like it to be.
In any case, thanks for the support.
a greeting