I have 8 machines all running on Duet2Wifi's with Panel Dues and identical settings. Two of them were plagued by this issues for the past year.
I was rebuilding one of them last week and decided to dig in an figure out what the issue was. I didnt think it was my router because all of them have reserved ip address. After hours of screwing with YAT and confirming that all the connections on the board were good, I cleared all the IP reservations and did a software update on my router. (EERO Mesh)
I was shocked to find that after the router firmware update, the issue was totally resolved on both the machines that had the issue. Not sure if it was the actual router firmware update, or the fact that I cleared the ip reservations and did new ones for each machine. Eitherway....the problem is gone.