Nuendo 8 crashes EuCon

system os10.13.6 (HS), Nuendo, Artist MCMix with Eucontrol 3.5.
EuCon would often loose contact with the MCMix hardware, so after reading positive comments on more recent versions, I updated to 18.3.244 (not the last one).
Eucon does not even see the MCMix anymore. So I did a complete cleaning of all Eucon files and reinstalled the software: no change. Last version (19.7.…) is no different. After a few hours of trashing Preference files, rebooting the mac and trying about everything including a fixed IP address connection without success, I reinstalled Eucon 3.5: now Eucon sees and connects to the hardware.
Looks good, but now the eucon app crashes when I launch Nuendo 8.

If it is a firmware thing, since recent Eucon apps do not see the hardware, I can’t access the firmware button in EuControl.
I have searched forums here and at Avid without finding any answer to the problem.
I’d be very obliged if anyone provided some help. Many thanks