I had a different issue with WLAN, which got solved with the help of #sailfishos-porters (thank you sledges and vknecht!)

• I installed m4r0v3r's initial image (the mega.nz hosted one), which worked fine. Well, as far as can be expected atm, but wlan was working.
• Unfortunately, that build did not have access to my Jolla account and the store, so I re-installed their second image (from the first post of this thread.)
• Wlan failed on this image (when setting up wifi networks, the SSID selector would just display 'switch on wlan'. I could tap that as much as I wanted, nothing happened.)
• Going back to the first image also did not re-enable wlan, so it was not specific to the image. After searching through dmesg, it seemed that the card was just not powering up properly anymore.

In the end, wlan got fixed by flashing back to stock android 6 (with the Android downgrade procedure from sailfishmods.de); then re-flashing sfos and it's still working so far.

I still have to try and reproduce, but my initial guess would be that it's linked to me trying to connect to two hidden WLAN networks with the same SSID, one on 2.4 GHz and one on 5 GHz. Detecting those networks is also not entirely stable, it usually doesn't see the hidden 5 GHz network even when sitting right next to the AP.