Info by R.Kammering (mail 20.9.23 18h25), related to the SA1 intensity drops during large wavelength scans:

"We found some problematic part in the code of our wavelength control server.
After lengthy debugging session we (Lars F, Olaf H. and me) did find a workaround which seems to have fixed the problem.
But we are still not 100 % sure if this will work under all circumstances, but this was the best we could achieve for today.
So finally we have to see how it behaves with a real scan from your side and if needed follow up on this at a later point of time."

Together with the finding of the test by FXE this seems to have resolved the issue.