Hello Paul,
You might need to be logged into your account on the MDA website in order to purchase a support ticket, although I'm not sure whether it's possible for a v4 installation, given that v4 is no longer officially supported.
My brief thoughts would be:
- Change the motherboard's battery if it has one. Even if the clock was correct when you checked, maybe it forgets the date/time erratically. (If the computer is sometimes connected to the Internet, then the OS will try to re-sync. the clock from a time server periodically, so you might not always notice a failing battery straight away.) v4's caches relied on timestamps (whereas v5+'s don't).
- Make sure Hauptwerk is always exiting cleanly. If it crashes (or if the computer loses power or crashes without shutting down properly) then settings files might be corrupted. In v4 the relevant timestamps were saved in the organ settings files and in the general settings file and compared. Check in the log that you always get the "Hauptwerk has finished shutting down" message preceding the next launch, which should indicate that it exited cleanly.
- Also make sure that you don't accidentally/sometimes have two instances of Hauptwerk running (e.g. if macOS is launching it automatically on boot). If two instances run, one will usually corrupt settings and caches of the other. If two instances were running you would also have a second "Welcome to Hauptwerk" message without the "Hauptwerk has finished shutting down" from the last run preceding it.
- Maybe the drive is failing, leading to the settings files and/or caches becoming corrupted.
- After Hauptwerk has launched, and after loading the relevant organ, check in the log that it doesn't report that the settings file was corrupted and needed to be restored automatically (which would happen from the last-known good backup of the file -- that backup file might have a wrong timestamp saved in it, e.g. due to the clock having previously been wrong).
- After checking everything else above (including changing the battery), force all organs to re-cache. I can't remember off-hand whether in v4 it was sufficient just to OK the "General settings | Audio outputs" screen, but in case it wasn't, and for good measure, insert a new dummy entry on that screen, OK it, then reopen the screen, delete the dummy entry, and OK it again. That would definitely do it, and will ensure that the correct current timestamp gets saved into the general settings file (and also into the organ settings files when you next load the the relevant organs).