My FP3+ shows since several month the same behaviour as described in an equal topic for FP2 (unfortunately never solved):
After awakening the phone from standby, it has no WiFi connection, but immediatly starts to reestablish it. It then does al lot of data transfer, which delays the possibility to interact with internet for a while.
The problem occurs also in safe mode, so it seems that no particular app is resonsible.
The Samsung Galaxy of my wife doesn’t show this behaviour.
When I’m not at home and within the coverage of another WiFi area, the problem doesn’t occur. Therefore I suppose, that it somehow is connected with my home WiFi network (FritzBox 7560 with mesh, Power-LAN and several acess points). I tried to switch off the mesh, and also switched off 5 Ghz band, but that didn’t do the trick.
Perhaps you can try with the 5G band only.
Or switch of your access points and try then to get connection with phone.
A long shoot reset your WiFi in the app Settings.
Use the search field with the word WiFi to find the right place. Remark: you will loose all passwords for WiFi and SSIDs and perhaps all your Bluetooth connections (on a Fairphone 5 at least, Is don’t have a Fairphone 3 at hand).
Anyway as it is a Fairphone 3 please make regularly backups.
Well, I’ve checked with 5G only; no success. I also have checked only with the router (without any additional access point) - no success. I have reset all networks (WLAN, bluetouth) - no positive result.
Since my wife’s Samsung Galaxy has no problems, safe mode (no any additional apps) didn’t help, and the problem occured November 2025 or so, it seems to me it’s a FP issue, might have to with the last Android update?