I don't think that the issue is related to multi-boxing. As far as I can tell is selective in a random way and seems more related to a specific account. Each of my toons are on different accounts and each is different in behavior. It seems I can play my TE or my TT without any issue, then I log my JE or my PS and in random timeline, not very long less than a 3 minutes, I get like a broken communication. I tried it on two different ISP's, but also on mobile data connection. Same results and the issue seems similar with the one from the last week that went away after the second server restart.
Stay safe and have fun!
PS After posting it, I relogged my TE and it behaved similar as I previously described my JE/PS and when I logged, it was already grouped with another unknow toon called Iced. This to add to the weird behavior.