One more point to draw your attention too. Under Ad-hoc mode, please make sure: if changing the IP address or Gateway address in the Quark-elec Configuration tool, remember that the ip address and the gateway address should be the same. Otherwise you will see an issue. More details can be found from:https://www.quark-elec.com/archived_forum/viewtopic.php?f=3&t=14025
So generally, when you have WiFi issue please consider the following points:
1, Does the device have reliable power supply?
2, Setup with static ip address if DHCP doesn’t work reliable under station mode.
3, Make sure the gateway ip address(setting with the configuration tool) is the same as your wireless router’s. If it works under ad-hoc mode, it must be the same as the ip address(server).
4, Change the port number from the default one(2000) to be a random one(e.g. 1437, or 2804…) on AIS receiver and the APPs.
5, Check if there is a strong WiFi signal nearby(this normally could happened in the marina, and there is ‘long range WiFi’ or ‘hot spot WiFi’).
6, If you have a VHF radio, please keep it at least 50cm away from the WiFi AIS receiver.
7, If your wireless router is a old type of two channels router(2.4G,and 5.8G), you maybe need disable 5.8G frequency(our WiFi module only supports 2.4G).

One more point is, if you only see the disconnection issue on Navionics. Actually, this is not real status of the WiFi, Navionics will show ”disconnected” if no AIS messages been received within 10 seconds, actually it still keeps connected.