I have the HP-250-3/400 planer combined with a thicknesser:
The thicknesser has a feeding mechanism which pulls the board into the machine at a constant speed, much like in this video: https://youtu.be/T4vl2IM1IJw?t=999 (similar machine).
The problem is that with my machine it works only for small planks. When I have a big board, I usually have to push it with all my might into the machine, otherwise it gets stuck and the rotating blade forms a "channel" in its middle.
I tried to vary the delta that is shaved off by the thicknesser, but nothing seems to help. What can be the problem and how can I solve it? My machine is brand new.
The feed rollers are parallel. As far as I know, they are set in a cast iron wall of the machine and they are not adjustable at all. I will do the narrow plank experiment as soon as I am with the machine again.
The feed rollers are a little greasy and when I set the thickness delta too large I see equally spaced (5mm space) grease stripes perpendicular to the piece.
By a big board I mean 150 x 20 x 3 cm or 60 x 8 x 1 inches. I will experiment with different sizes soon.
There is a handle to start the feeding rollers. This is just an on/off switch and I make sure to have it turned on. There is a lever that needs to be released before one adjusts the height of the bed. I tried both with the lever locked back into place and the lever released. It seems that the thicknesser bed is resting on a set of strong springs and that there is some allowance to the movement of the bed - meaning it is not absolutely fixed to the rest of the machine. It can move a couple of millimeters. This allowance is diminished when I lock the lever.