drinkingbird
Part of the Furniture
It was also discussed in this thread:
https://www.snbforums.com/threads/arp-problem-between-wifi-devices-on-rt-ac88u.81665/#post-808189
So it is only wireless devices having the issue? There is definitely more potential for problems there, for some reason thought we were talking wired having the issue too. But again it must be something related to certain configurations since it is not everyone having the issue. I'd check the release notes and see what changes were made between the version that works and the one that doesn't, maybe wireless driver got updated.