Slow Wifi on AP (Fritz Repeater)

Installing and Using OpenWrt Network and Wireless Configuration
1

Hi all,

I have recently posted here: No DHCP on Guest Wifi

Unfortunately I'm still facing the issues: The Wifi is slow or not reacting. The setup is still like suggested with No DHCP on Guest Wifi - #3 by psherman, a reboot solves the issue.
As I'm using the Repeater with 2 SSIDs and related VLANs I was wondering if the issue can be more related to

  1. Issue with multiple SSIDs on the radio level
  2. Issue with VLAN handling

Related to the second point: The repeater I have connected to my OpenWrt Router, so I can exclude any components in between.

Any idea how I can analyse the issue?