Port role for LAN2 causes network loop

PeterUK

USG FLEX 200 V5.38(ABUI.0)

I may have to do a part draw out part of the network if needed but when I have LAN2 for Port role on FLEX 200 to the WAN2 of my Zywall110 it causes a lockup of zywall110 but if I unplug LAN1 on either FLEX 200 or Zywall110 the problem does not happen. BUT if I use reserved for Port role on FLEX 200 then connect that to WAN2 of zywall110 no problem.

Its like LAN1 and LAN2 are bind when they should be isolated on FLEX 200

PeterUK

Here are two layouts the first causes a lockup of zywall110 caused by FLEX200 port role in LAN2 the other does not have a problem