Hi Harald,
Please see the pcap files in https://people.osmocom.org/laforge/pcap/
specifically https://people.osmocom.org/laforge/pcap/osmobsc-nanobts-efr-dtx.pcap
The server returns "403 Forbidden" for the linked file and for most other pcap files in that directory, including most interesting ones.
[sysmoBTS FACCH issue]
I would agree this is a bug. Irrespective of whether you have a (hacky or not) patch, it would make sense to have this in the osmo-bts bug tracker.
OK, I will write up the bug issue.
To my big surprise, my Osmocom setup worked fine with the nanoBTS i have (model 165AU, DCS1800). I'd have expected more bit-rot given that we don't know anyone regularly using such a setup anymore.
My first attempt was almost a year ago in 2022-04, using a PCS1900 unit. I posted my pcap file on the ML, you looked at it and told me that there seemed to be a problem with TA control loop. Yesterday I tried with my GSM850 unit and the behaviour appeared to be the same.
There was one bug in osmo-bsc I had addressed in https://osmocom.org/issues/5959
Does your fix make the difference between the setup working and not working? IOW, did it work prior to your WIP OS#5959 fix? If the setup worked even before that fix, then it probably won't fix whatever issue I am having here.
M~