By the looks of it I'd say the gnss-sdr source is the problem, does the
count keep increasing or does it stop at a certain number?
The explanation for the latter would be that the Application connects,
but does not read, rtl-tcp has no starting or stopping. As soon as a
client connects it tries to pump out samples until the client
disconnects, so buffers are going to pile up if there is a delay between
connecting and reading and the count will stay the same if the
application does not read the data faster than real time to empty the list.
If it keeps increasing the most probable explanation would be a sample
rate mismatch or some other reason why the client does not read fast enough.
The "known to work" rates are just that - values that are known to work
without any side effects, but most other rates should work, too.
Frequent tuning, gain adjustments, or other commands might cause those
commands to pile up, but neither of those would cause the dongle to
produce more samples than anticipated unless your app accidentally sends
out a command to set a higher sample rate...
- Hoernchen