I cannot reproduce with -Q, but evaluating
`(x-synchronize t)' sometimes garbles display.  See
attached screenshot.  Note: When copying the region
shown in the screenshot and pasting into nano, the text
is correct, not garbled.

Evaluation of `(x-synchronize t)' is part of the
attempt to capture a usable backtrace for bug#66978.

Now this display bug is another one.  If you have any
ideas how to investigate these I would be happy to help
following instructions.

Thanks, Gregor