If their network was bad, they wouldn’t have low network ping. If it’s the game then working in some servers but not others is kind of strange, especially considering these are fairly popular games. I believe it’s something else 
@rikebadban are a decent amount of players in the servers that this happens in? Also, when this happens, is your ping changing or is it staying the same number? It’s hard to tell because of how short it is, but in the SCC clip your ping seems to “freeze”, possibly indicating a silent disconnection, which is an issue that’s been a thing for a while
It actually may be related to the region, as I found a topic with a similar issue:
Next time this happens, try waiting a minute and see if the game starts working.
Other (possibly) related topics: