disconnect stations in Access point

hi
i have a mikrotik sxt SA5 at mode AP The 6 stations connects to it
sometimes stations be disconnect Automatically and until That wireless card disable/enable do not stations do not connect
please help me?
log sxt sa5

try upgrading devices to routeros 6.40.5 then upgrade routerboard firmware (will be 3.41)

I do updated
I change frequency?

What happened after the upgrade? Did it help?

It did not change