link extension(vpn)

This is the toplogy of my link extented to get a customer where the base station can’t reach.

For my repeater site i used a SM and two AP’s connected in a wireless cisco router.
This is my repeater link configuration:

AP0 in the CMM 172.25.12.1

sm 172.25.12.2
AP1 172.25.12.4
AP2 172.25.12.5

sometime all canopy’s pluged in the wireless router time out at the same period with same duration(time) almost 30-45 msecond,while the AP0 in the CMM has no problem.
or AP1 and AP2 are timing out at the same time while the SM 172.25.12.2 is pinging perfectly the AP0.
I would like to know what can be the main problem then how can i do to solve it?