Hi Jose and Sigi
I can relate my experience with the LimeSdr USB
Do not transmit anything near the max power out.(signal is way distorted then)
I set it to -20Dbm (so needed another amplifier in the chain to reach the 2.4 Ghz for the Qo100)
But then it does not get stuck, no central spur (I use 250 khz offset) and see no spur anywhere on the full band of the Qo100) (peak signal when modulating with a single tone S9+12
and nearly 37-8 S/N).
BTW Jose I use now the X8 resolution on the waterfall and then you can see very accurately any Jitter in your signal, and mine is very similar to the band edge Beacon. If the 'lock to Beacon' is wobbling (a bit, not complete unlock) the you'll have wobbling on your TX freq.)
De Joe 4X1RV