So story is going on. During these three nights, I had many disconnections, and many command failures. I modified the eqmod driver and increased the retry count from 3 to 8, and that solved the failures.
But that doesn't solve the core issue. The driver is more robust but the mount behavior is still instable. There are sometimes as many as 6 iterations to get to the target. Guiding is terrible, with strange bumps, mostly in DEC.
But in fact, recently I changed the power supply that was feeding the entire setup, and I found that the new (crappy) model produced a 100Hz 2V DC ondulation when load was connected. This is especially visible when the dew heater starts. This supply instability is probably the root cause of my problems. The previous one was not powerful enough to drive the dew heater, but the new one will require an additional voltage regulation after the heater module.
HEQ5-Pro - Atik 314E - Orion ED80T - DMK21 on Orion 50mm
DIY 3D-printed Moonlite and FWheel RGB/LPR
KStars and indiserver on two Atom 1.6GHz 1GB RAM Linux, VPN remote access