ZF2942 - SSID password becomes corrupt

unknown

I have an old ZF2942 in AP mode running (standalone), and at first it seems to be working fine. But after a while the Wireless (1) becomes unavailable.

After resetting the device or reconfigure the SSID password, it works fine again. 
The device on version 9.7.0.0.220.

Anyone had the same issue? Maybe some tips or tricks on how to fix this?

Thanks in advance!

Kind Regards,

Jerome