After I resume my Windows 10 laptop from a sleepy state (or after rebooting), it can't reach one of my Raspberry Pi computers for some time. IMAP doesn't work, no ping, nothing. After a while (5-10 minutes) this "restores itself" and I'm able to connect to the Pi.
The laptop doesn't have this problem with my other Pi. This one is also on the same network, but can be pinged and reached without any problems.
Also, if I ssh into "working" Pi (WP), I am able to reach "problematic" Pi (PP) without any problems from there.
Also, my Android device has no problems reaching PP whatsoever.
Both Pis are on a WiFi connection, the only difference I can think of is that WP is also on a wired connection (but it can be reached on both IP-addresses).
I have looked into the Windows firewall settings, and added a very liberal rule for allowing traffic to PP. It didn't help and even if it did, I would still be in the dark about why there is no problem with WP. Also I changed the WiFi settings on PP so it won't go into sleep mode, but this doesn't fix the problem, and even if it did, I would still be in the dark about why my Android phone and WP don't have trouble reaching PP.
Does anyone have any suggestions what can be the cause, how to solve it, or at least how to troubleshoot this?