Dodgy amplifiers?
So far they've deployed 4G in areas with good signal levels, where generally amplifiers are not needed. When they deploy in fringe areas away from main transmitters, that's when they'll find problems. As the signals are inside what has been the UHF TV band, it's in the pass band, even ones that are TETRA proofed. Pity the poor folk getting a free filter, but then it needs to be fitted between the antenna and the masthead amp at considerable cost.