For the past few years, I have had no issues with visitors using my guest network.  Recently, out of the blue came an update (I thought this system was out of support).  When selecting the guest network, the system gets stuck on "obtaining ip address" then reverts to the main network.  I have discovered that if I am connected to another M5 on the same network, switching is ok.  I have six M5s on my network and all go through an unmanaged bridge.  I swapped out the M5 for another and the problem persisted!.  So, in summary, this only occurs at a certain network point and it only started after a recent update.  Do any gurus have a suggestion as to what is happening?

Thanks