Users keep getting logged out every few minutes

Hello world !!!

I have got a strange problem :
Some wireless hotspot users are logged out every few minutes.
Log says :

hotspot,info,debug yk4 (10.128.30.60): logged out: keepalive timeout

keepalive-timeout is 10m

As far as I understand things, this looks OK. But also active users are logged out and
the users have to login again.
Normally a user just has to reconnect and is lgeed in automatically if an active
cookie exists.

cookie-lifetime is 3d

Users complaining about this are all using mobile devices (cell phone or tablet)
Notebook users seem not to be affected by the problem.

Can anyone give me a hint ?

TIA

Wayne

no ip Bindings put the range of the pool and puts regular, on the bottom line put 0.0.0.0/0 blocked so the entry in the hosts will only be that of your pool and will solve your problem

/ip hotspot ip-binding
add address= (ip pool)
add address=0.0.0.0/0 type=blocked