It's all about the Software

Hi there, console has been working fine, with QO 100. I use the geo beacon to lock my LNB ( modified high stab xtal oscillator, so generally of by about 10kHz max.) No problem, but tonight the beacon lock keeps drifting off, I re centre it ok for a bit, then breaks lock and drifts off.
Any ideas, please?

Screenshots always help, the beacon does get jammed at times.