Looks like I’m the only one having these issues :-). Just in case anyone else comes across this post, here are some findings so far.
For the first problem, I have set the OSv3 unit to have a fixed IP. It was already a ‘reserved IP’ in my router settings, but the settings on the unit itself were DHCP. I changed to fixed with the same reserved IP as I had on my router. So far so good, the last few programs have run without errors.
For the second issue, I added a fan as mentioned, but that just draws down my battery too fast, so will ditch that idea. I found a setting called Boost time, which I increased to 800. This has helped and most of the solenoids turn off reliably. However, one particular station was only turning off every second time I ran it (very strange!) so I moved the wire to a different spare station and it’s so far working fine. I guess the original station port had something wrong with it.