I had my first experience of this last night while i was playing with a group of about 5 or 6 friends.
It seems as some say that it only happens when you're close enough to a certain player but I don't want to play on other servers since it ruins a huge part of the game for me if I can't play with my friends.

I have a 100/10 fiber connection and haven't experienced anything like this in any game including DayZ SA until yesterday so it seems as if it some change ingame is the reason.

Dunno about "mainly" because me and most people I know personally(who has experienced this issue)have great to atleast decent dl speeds.

I've got 100Mb dl speed on a fiber connection and I can experience this on a close to empty server with only 1 or 2 other players close to me.