Weird.
I briefly had a similar experience two days ago. The network LED (opposite side of the charging LED) suddenly lit up in magenta and just stayed on. Then it began flashing, went back to steady magenta, seemingly repeating. Picking it up, I noticed it had dropped from 4G to 3G, and seemed to stay there. Inches away, my other phone, with a SIM card from the same (Swedish) operator, had seemingly stable 4G reception. As I was in the midst of a meeting, I found the flashing annoying, so I went to flight mode. Later, when leaving flight mode, I was back on 4G again, and I haven't experienced it again.
How are things going on your end? Still just 3G?