@Pêcheur , reviving this thread as I had a break through on this earlier this week. I kept looking to resolve this as I hated having a mesh satellite in my tank stand. Hoping this works for you too. It has been 3 days of continuous wifi connection w/o a disconnect and I finally think I figured it out.
in short, the problem was that the Apex kept it's original IP address after reboot and router reboot. So after my router rebooted, another device took the same IP address as the apex while it was offline. So when I try to connect the apex to the network, it would for a while and then disconnect when the conflicting device connected with the same IP address ( was also on the same 2.4hz network). This is my theory and why I would get random disconnects happening ranging from hours to days.
The fix: Per Neptune's help desk, I downloaded the Apex browse utility program. See screen shot of it. This program is a lifesaver. What I was able to do is manually assign an IP address to the apex. I chose it to end in .99 as the other devices start at .01 and work up in number. previously it ended it .26 and was conflicting with another device with the same address.
Restarted the apex and confirmed with the router that it sees the apex on .99 - see screen shot.
After that, it has been working without a hiccup. On day 3 with solid connectivity and the best part, without having to use a satellite in the stand to run an ethernet cable to the apex.
hope this helps and works for you.