nbc dt 14 breaking up with good signal please help

[Playaction]

nbc is breaking up with 80 % and above while fox and abc hardly ever break up and they are in the 60's. I assume all are uhf.
epuipment-942
8 bow antenna uhf
titan uhf/vhf amp-it is set to uhf and the trap is off.
my zip is 36078

I had a uhf/vhf antenna before and nbc was fine but I could not pick up other stations so I switched to uhf antenna. I tried a joiner to hook up to both but it does the same thing.

 

[Jim5506]

The signal may be strong enough that you are receiving multipath reflections that oscillate in and out.

Try tweaking your antenna slightly left or right and see if that helps.