I also run a zone over a TPLink powerline adapter which prior to v2.435 used to drop out frequently. I thought it might be due to the TPLink going into power save mode when there was no traffic over it causing Sooloos to drop the zone. Anyway, I just got used to switching the zone on only when I wanted to use it as it never dropped out when playing music.

On reading your post I decided to try keeping it powered on full time. I'm happy to confirm your observation - the zone has been up now for over three days and I'm very pleased it works just as it should now.

Main: 861v8+ID41, 218, HD621, DSP8000SE u, DSP7200SE u, DSP7200HCSE u, Oppo BDP103D, LG OLED557BV.
Second: 218, DSP3200, DSW.
Other Rooms: 1) F80 + MS200. 2) F80 + MS200, 3) F80 + R Pi. 4) F80 + R Pi, 5) F80 + R Pi
Vintage: 207 CD Pro, Lecson AC1 + FM1 + AP3 MkII, Quad ESL 57s