Hi,
i ran into this Issue, here was my Workaround, it works also after a reboot
track 3 ip sla 3 reachability
ip sla 3
icmp-echo 208.67.220.220 source-interface Vlan20
owner SAM
tag Ping to Internet SLA 3 208.67.220.220
frequency 10
ip sla schedule 3 life forever start-time now
event manager applet RESET_AP
event track 3 state up
action 01 cli command "enable"
action 02 cli command "service-module wlan-ap 0 reset" pattern "confirm"
action 03 cli command "y"
action 04 cli command ""
action 07 cli command "end"