Network Issues after upgrading to 23.4.A.0.546

Just as the title says. After updating to 5.1.1 I noticed that I'm getting a terrible network signal anywhere I go unless I'm directly outside.
I could be inside a building near a window and my network will be 1 bar or even less sometimes.

Is there anyone else experiencing this? Is there any way to fix this?
I flashed the Greece version and then updated with my local baseband and kernel etc.

Thanks.