90002 Error when near my character is near one specific player

So I've been having a reliable recurring 90002 error that's pretty strange.

When I'm playing alone, no problem. If my husband, who is plugged into the same router, sitting about eight feet to my left, starts playing, we get problems. But only if we're both in a Heavensward "combat" zone. Both in a "Realms Reborn" zone? No problem. I'm in a Heavensward zone and he's not? No problem. He's in a Heavensward zone and I'm not? No problem.

But within a couple of seconds of us both being in a Heavensward zone, I get the 90002 error and get kicked. Log in, and get kicked again. He moves his character to Foundation or some other zone, and I can log in just fine.

And the entire time, my internet connection isn't disrupted.

We've played for weeks together without this kind of problem, it's only in the last week or so when we got to Heavensward content that this annoyingly reliable 90002 error started popping up.

Any suggestions?