pepvpn UDP ports

I have a Peplink Balance 380 (6.3.4 build 3613) that serves up 3 “PepVPN with SpeedFusion” links.
Client 1 is a Peplink Balance One (6.3.4 build 3613).
Client 2 is a Pepwave MAX On-The-Go (6.3.4 build 2625).
Client 3 is a Peplink Balance 30 LTE (8.2.0 build 5312).

I noticed that Client 1 and Client 3 would experience VPN drop-and-reconnects every few hours. Oddly, they seemed to occur on both clients at roughly the same time (within a minute). Client 2 was stable.

I fixed the problem (it seems) by setting unique custom Data Port values on each link. They are all stable now.

Is that normal? Or some sort of known issue?

We’ve not seen that absent WAN issues. That’d be my first guess. I’d also update each router’s FW to the most current.