DOS 2.9.0

[DesertEagleAZ]

PLC you mean? Have you tried ethernet to see if it fixes it?

Am becoming increasingly worried about deciding to give Devialet another go

I have not tried Ethernet yet but i will give it a try. 
If i plug my iMac to ethernet too, does it mean sound will travel through ethernet and not airplay anymore ? I suspect Airplay to be unstable...

AirPlay has nothing to do with means of transport. You can use AirPlay between a Mac and an AirPlay endpoint if both are connected via Ethernet. My Golds, in fact my whole system, has been rock solid ever since going back to 2.8.5 using AirPlay with Roon playing to six (!) endpoints simultaneously. Two of those endpoints are Devialet speakers in stereo as indicated below