WilsonPro booster works for 3g but fails for 4g?

I have a WilsonPro M2M Booster (Model 460119) connected inline between my netgear LB1120 and my outside Yagi antenna. when the booster is off, the netgear shows a signal strength of around -115db for both 3g and 4g. On 3g, when I turn the booster on, the signal improves greatly to around -75 to -80 and is slow but usable. When I switch to 4g, this signal strength also shows around -75 to -80, but after 30-90 seconds drops back to ~-115 and is unusable. If I unplug the booster and plug it back in, the strength again goes to -75 to -80, but again drops back to ~-115 after a minute or so. This is very repeatable, always works after power cycling but quickly stops working.

Anyone have any thoughts or a direction I might be able to go for troubleshooting. As I said, with the booster the 3g is fine but I'd love to be able to get the higher 4g speeds if possible.

Thanks,