Guest Wifi user password authentication failure(Token)

unknown

Good day, has anyone come across the following issue before? We have a Master AP and 3 Slaves, all slaves work fine apart from one, for some reason the corporate Wifi is fine when connecting through it but the Guest Wifi does not authenticate any tokens,  this only happens in the one area, if I move the same AP to another area I have no issues. We changed Ethernet cables, changed ports and connected the ac adaptor so that it did not get data and power from the same cable, yet no difference, the firmware is up to date and settings the same as the other Slave AP's. I have run a 50 metre CAT 6 cable from the main switch in the server room to the main up link port of the switch where the AP is connected just in case the cable is damaged or the Cat 5 was experiencing any degradation issues and got the same result as before. - Any ideas please?  Thank you.