band search on Uhf

I was searching the 450-470 Mhz today with my Uniden 996xt and it would always stop on a frequency with a noise on it. I would have to lock out from the scanner to get it to scan again. My question is what causes this?

Trunking control frequency, interference around the scanner [computer, TV cable, LED lights, etc.]. Could be someone with the mike button pressed by accident. There are many reasons. IF it was in the FRS/GMRS frequencies, could be someone taped the mic button so it was a continuous transmit. What frequency was this on? What is location. These last 2 are important as someone familiar with the area and frequency could help. And they could do a FCC database search. So more information might help to narrow it down a bit.

I seam to find it in the 450-470 frequency range. It's on serve frequencies that I have to lock out. I was told, but not sure if this is true that some companies have equipment that makes noise so you won't listen to them. Yes it's on Gmrs frequencies.