Who I have the same questioned this topic

Yes I did check the modem as well. I restarted it, cleared the cache for all my apps and I'm still having the same problems. Just like others mentioned here already it looks like some apps aren't working properly. I know Facebook for instance is not working properly on the phone. But there are other apps too. But when I switch to mobile data they all work properly. I even re-installed some of the apps and it did not fix the problem.

Thanks,