Tvheadend

Hello,

I have been running Tvheadend successfully on Synology NAS for a couple of years, but now I am stuck and would really appreciate some suggestions.
Version is one of the latest from http://syno.dierkse.nl/, doesn't really matter which. All current Tvheadend-testing versions tried, so 4.1-2116-1 or 4.1-2140-1 are the two latest ones, same symptoms for both.

Problem occurred after upgrading to 4.1-2140-1 from an earlier build, I believe it was 4.1-1945-1.

NAS is Synology DS2015xs, latest DSM6 OS (6.0.1-7393 update 2). Tvh package for Synology Alpine architecture.

Symptoms:
- Unable to log in with admin/admin or user/pass created during install (solved with inserting C switch in startup script)
Creates users and other configurations in GUI, then crashes after a while - won't restart
- Restart of NAS gets it back up, but config is lost. No users, no networks, all back to default clean install
- Adding new admin user(s), save and stop Tvh before crash occur does not change anything. It will restart, but config/users are gone. Login without -C impossible.

I have uninstalled and reinstalled several times, different builds. Same thing happens.

So either I will need to clean out some files/setting or something, or I will have to factory reset and reinstall the NAS with a fresh DSM OS.
I suspect there are some old files and/or settings from previous Tvh versions that is creating issues. Is there a way I can clean out everything related to Tvh? Where would it be?
Removing old files/settings is preferable, as fiddling around trying this and that has and will take even more time than a full factory reset/reinstall, after all :-)

Any other ideas?

Thanks for any suggestions, it is greatly appreciated!