The HR10-250 has a known issue with flooding from the IR flasher. People keep posting this question again... and again... and again!

Move the flasher away from the eye. Move it away in 1/4" increments until you get reliable control. Yes... it won't be directly over the eye, that's the idea here.

If you had a MRF-300 you could turn the gain down.

Has anyone ever tried the 3.5mm IR jack on the back of the unit next to the RJ-11 phone jack? The manual says it is for "Future Use" but thought it might be connected.