I replaced the 2 files any way and the green pulsing line disapears. The main media that it happened on was live TV from TVheadend in NZ. most of the broadcasts are in 1080i. there does appear to be some image instability, light shimmering on certain elements in the frame that are not present on a Rpi 5 so will probably recycle the 4s and replace them with 5s.
