Have a XS3800-28 acting as the campus core switch at a single location connecting to individual XS1930-12HPs which have connections to a USG Flex 500 and multiple WAX650S, WAX610D, and one WAX510D (8 total). Two pairs of OM4 fiber connect at 10GB each to each XS1930 to the XS3800. If we have just one pair between these switches the AP Management on the USG Flex 500 works fine. Adding Link Aggregation (without LACP) using src-dst-mac with both pairs combined with Rapid Spanning Tree typically kills the AP Management within 24 hours (the APs are still usable by client devices, but CAPWAP errors for "AP Disconnect." "Reason: Idle in RUN state" appear in the USG Flex 500 log). Disabling one of the two links per XS1930-12HP also kills AP management for the APs connecting through the LAG. APs operating without a LAG link between them and the USG Flex 500 will continue to work fine. Had same errors on LAG using copper link. (Some Zyxel switches have been left out for simplification. All equipment on the latest public firmware. Not using Nebula). Suggestions to fix this? Questions? Thanks

All 8 APs are properly shown in the USG Flex 500 AP Management List (most are doing two LAG hops). Thank you very much Zyxel_Chris for your help and the patched firmware. Please close any tickets you have on this.

Update: The root cause is on XS1930 with LAG interface (traffic send to the wrong interface cause the traffic lost), this case has been resolved by the datecode, the official release will be on December (f/w: 4.70).