Too bad it's a state license as it makes it more difficult to map potential changes without local knowledge - perhaps there is some relevant RPC correspondence. We'll have to assume the issue is interference from a new LTE site fairly close by, but not hideously close - I had a cell site 500' away that I could see out the window of my office but didn't suffer any ill effects (except possibly drowning out distant systems). Experiment with new antenna placement, a directional antenna, and / or buy a high pass filter. Or get a better receiver.
We had an issue with a Verizon LTE site (talk-out side) interfering with portables in a small town, with a secondary source from Axon body cameras (talk-in side). This will ultimately be resolved with a new system site in the area where the interference is being experienced. The FCC is aware of Band 13/14 LTE interference nationwide, but lots of finger-pointing going on. The carriers say their infrastructure sites are in spec and the system manufacturers need to design better radios, ignoring that their customers are not always using the best quality cell phones (or body cameras). We do need better receivers in general however.