Good day, with Mikrotik we work for more than 15 years and now we have huge problems with the new device: RB922UAGS-5HPacD
Ap are in an ungrounded environment and have a packet loss on a WiFi subscriber of about 15-30%. This error rate has all APs.
turn on FlowControl did not help, tested with the latest firmware: 6.43.8 We can give you access to our site for testing!

Wireless can’t have packet loss if link is stable. Check the log, if the client is simply not disconnecting because of poor signal.
Use nv2