Hi Johan and Stefan!
I had the exact same problem as you. And thanks to you, it found out to be a problem with F-Secure.
Luckily, my cousin works at F-Secure and I showed this thread to him if he could find out a better workaround. He asked me to try disable DeepGuard from my F-Secure.
I rebooted my laptop after disabling DeepGuard and now it seems to work alright.
I've now only tried this once, so I'm not 100% sure if it works in the future, but I think you should give it a try, too.