gray artifacts in the video. 25 frames on TV

Hey.
I have had a problem for a month.

I record videos in 50 frames in FullHD quality.

I'm rendering a project in 25 format.

So far there have been no problems. After rendering at 25 frames on the computer it is OK, but on the TV gray artifacts appear from time to time in some places.

I have been making films for several years, but this is only happening now.

50 frames on TV is fine.

Am I making some mistake while rendering?