PC, desktop (Windows 7) and laptop (Windows 8). I always play the web version so I have the latest one. I did play the downloaded client for a while in 2.85, IIRC, and I never had a problem there. But I didn't play on it too much. I haven't been playing too much for the past month or so though, either so take this as for the months preceeding.

Disconnects are rare when I'm playing on a computer, and most (probably 9/10) of the times its when my wifi craps out for a second when I'm using a laptop. But it stays disconnected even if I reconnect immediately, and the timer... Thing keeps ticking down.
So far I haven't really paid attention to JUST how often they occur. When it gets really bad is when my wifi is spotty, so the only thing on your end there is the (lack of) re-connection

I think I got out of that timer ONCE, but I'm wondering if it was a fever dream or something because I've never had it happen again.

I do get sync errors and regular disconnections from time to time as well. No rhyme or reason to it as far as I can tell. They're much more uncommon than the wifi based ones. Not enough that I pay a huge amount of attention.

I have noticed that sometimes, when things freeze up and I'm wondering if there's a disconnection, there's a card my opponent has played hovering below my own hand and clicking on it will continue the game. Seems to get stuck there during the animation of it showing up when it's first played (how the cards are usually revealed by being held out to the top view thingy, if that makes sense. It does that after I click on it.)

Anyways, hoping my random feedback is useful - and thanks for what you do for the game, Gondorian.