[SOLVED] SSH connection sometimes hangs

I have disabled Wifi power management (adding sudo iwconfig wlan0 power off in rc.local) but the SSH freezes/disconnections still remain. I’ve also checked power management status:

osmc@osmc:~$ iwconfig
eth0      no wireless extensions.

wlan0     IEEE 802.11  ESSID:"ODPEGOF"
      Mode:Managed  Frequency:2.412 GHz  Access Point: 30:91:8F:7C:2B:BD
      Bit Rate=65 Mb/s   Tx-Power=31 dBm
      Retry short limit:7   RTS thr:off   Fragment thr:off
      Power Management:off
      Link Quality=62/70  Signal level=-48 dBm
      Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
      Tx excessive retries:0  Invalid misc:0   Missed beacon:0
lo        no wireless extensions.

so I’m sure that is effectively disabled.
I’m able to ping the raspberry even when experiencing SSH freezes and samba shares are accessible and files (in my /home/osmc or in /media) are readable & writable. Only SSH connections have problems.

What else can I do to track down this problem?