list of possible causes of the high frequency noise which makes the system loosing the lock => to be checked.
(if you have some new idea, I will edit the post)

1- Laser
   1.1- vibrations on the laser box coming from the optical table / housing
   1.2- vibrations coming from the Smaract translation stages (Frep or CEP) inside the laser box
   1.3- pressure noise coming from the weather (the laser cavity is sealed) on the laser box

2- Amplifier
   2.1- vibrations coming from the fans in the controler crate
   2.2- vibrations coming from the chiller (water cooling cavitation)

3- Beam propagation
   3.1- vibration noise coming from the housing / the table
   3.2- vibration noise coming from the motors of the injection mirrors

4- Fabry-Perot cavity
   4.1- pressure noise on the cavity vessels coming from the weather/air cooling
   4.2- vibrations coming from the rust on the mechanics
   4.3- vibrations of the mirror mounts due to temperature related to cavity power
   4.4- vibrations coming from the electron ring mechanics
   4.5- "vacuum" index variation coming from local ionization due to the electron beam
   4.6- vibrations coming from the far position (related to the middle range) of some mounts and due to the spring of the translations stage.

5- Feedback system / Electronics / CEM
   5.1- CEM votage noise on the laser or FPC PZT's