Okay. This annoyed me so much, since I used to have beacons on 3 of my old residences. I had all of the iron blocks and no blocks were blocking the beacon. I opened up the GUI and bam. Nothing happened. I asked other players and it worked for them. I even asked staff to help, but it also worked for them. I felt so stupid. I abandoned using beacons after that incident, but I forgot to post a thread about it. Someone smart answer the problem.
I still come across this annoying bug, when I'm out and about in the wild mining away. Though you actually don't even have to break and replace it. Just keep right-clicking until it appears normal - works for me every time and my pickaxe stays happy longer. ~ Just saying