Tank indicators are a common issue with most every camper from what I can tell. There are lots of threads here with advise on how to resolve issues.
We use TST as well and have only one or two instances of bad odors. Have you checked to make sure the toilet is sealing completely when it is closed? There should always be a little water in the bowl as well.
'17 Winnebago Vista 31BE / Wife, pesky Eski and loco Toto dog
'15 Open Range 256BHS / '05 F350 CCLB RWD V10
'14 Keystone Passport 238ML / '13 GC Trailhawk Hemi
RIP Birch (pitbull)