Cell signal strong outside, weak inside the rig

A big difference between signal strength outside versus inside the rig points to the rig's own metal skin and low-E glass blocking a meaningful amount of signal — this is extremely common and not a sign anything's wrong, it's just physics. A properly installed booster with an outside antenna and inside re-radiating antenna is built specifically to solve this. Do you have a booster installed currently, or checking if you need one?