STA disassociated from AP

After several hours of perfect operation , my STA´s are disassociated from AP with this code “Reason: 33 (GPFs MISS)”. I don´t know what happen. while the link its up the operation its ok, but when the STA is desassociated then i need restart the AP for the new association.

Can you help me?

I have epmp 1000 with firmware 2.1, one AP and two STA

GPFs missed means the SMs (STAs) were not able to receive control messages from the AP for consecutive frames. Control messages are sent over the air at the lowest (most robust) MCS which means that the RF environment is changing due to interference and causing problems. There are several things you can do such as increasing Tx power, Target Receive level, better alignment etc. Please contact our support engineers @http://www.cambiumnetworks.com/support/contact-support if you’d like some assistance with troubleshooting the link.