HA strange behaviour, web not working

Hello can someone help me?
I installed new RPI 3b+ with latest hassbian image of HA, do some configuration and sensors… (cable lan connection). But HA is working for about maybe a day, then it is not reachable from web browser… only I can connect thru SSH… this is LOG output from command:
sudo systemctl status -l [email protected]

what is strange. also I was trying HASS.IO image on RPI ZERO W, and looks like same behaviour… both are latest version of HA and HASS.IO… (wifi connected to lan)

I got my “old” hassbian RPI 3 working rock solid fine on HA ver 59.2. so it is not network issue…

[email protected] - Home Assistant for homeassistant
Loaded: loaded (/etc/systemd/system/[email protected]; enabled; vendor preset: enabled)
Active: failed (Result: signal) since Wed 2018-04-04 03:17:20 UTC; 15h ago
Process: 6801 ExecStart=/srv/homeassistant/bin/hass (code=killed, signal=ABRT)
Main PID: 6801 (code=killed, signal=ABRT)

Apr 04 03:17:15 hassbian hass[6801]: File “/srv/homeassistant/lib/python3.5/site-packages/homeassistant/components/device_tracker/nmap_tracker.py”, line 102, in _update_info
Apr 04 03:17:15 hassbian hass[6801]: scanner = PortScanner()
Apr 04 03:17:15 hassbian hass[6801]: File “/srv/homeassistant/lib/python3.5/site-packages/nmap/nmap.py”, line 131, in init
Apr 04 03:17:15 hassbian hass[6801]: os.getenv(‘PATH’)
Apr 04 03:17:15 hassbian hass[6801]: nmap.nmap.PortScannerError: ‘nmap program was not found in path. PATH is : /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin’
Apr 04 03:17:15 hassbian hass[6801]: >
Apr 04 03:17:20 hassbian hass[6801]: 2018-04-04 03:17:20 INFO (MainThread) [homeassistant.core] Bus:Handling <Event state_changed[L]: old_state=<state sensor.processor_use=4; friendly_name=Processor use, icon=mdi:memo
Apr 04 03:17:20 hassbian systemd[1]: [email protected]: Main process exited, code=killed, status=6/ABRT
Apr 04 03:17:20 hassbian systemd[1]: [email protected]: Unit entered failed state.
Apr 04 03:17:20 hassbian systemd[1]: [email protected]: Failed with result ‘signal’.