In that case I would test whether the situation is improved in the LE9 millhouse builds.
I have two MyGica T230 sticks too which work just fine for me under LE 8.2.3 on my Generic machine, though I use DVB-T2 rather than DVB-C which could be the difference.
Presumably, you've only enabled DVB-C in the TVHeadend adapter settings and have not enabled DVB-T?
Yes - I only use the DVB-C tuner in TVHeadend. I lightly overclocked the RPi3 now and seem to get less freezes - but still once in 10-20 minutes, where picture and video freezes for a few seconds.
Which logfile could I post here to possible get some hints in the right direction here? Maybe the service.log from the tvheadend-folder?