grain not cracking

[panadero]

Hello, I have a jimboney malt mill, 12 inch rollers. It has a fixed width between the top two rollers, and the third one is adjustable. Some of my malt goes through easily, while some just refuses to break. I have it set at .040 mils. I am running my pale malt through twice today, and it is still not completely breaking up. It is cracked inside the husk, but the husk is not coming apart. This happens with biscuit malt as well. Darks and caramels are milling perfectly.
Question - is it the malt, or the mill? I have adjusted both front and back set bolts. Doesn't seem to be room for the malt togo around the rollers, but...
Any feedback on similar experience, or about the mill in specific will be welcome. Not sure where my issue is.
Thanks,
David

edit: Clarification. I was having the issue slightly with just a certain pale malt, but am starting to see problems with others as well, which is making me question the mill rather than the grain.

[panadero]

I took the mill apart to check the adjustments - hard to reach up with feeler gauges - and while the marks may be slightly off, it seemed fine. The top two rollers are geared together, and the bottom roller crushes the grain against one of the top rollers. The bottom roller is adjustable, but not geared. It seems that as I make the gap smaller, the other side is getting wider. Wider than the gap between the top two - which is roughly 60 mils. My conclusion is that the harder kernels of grain, taking longer to go through the two crushing rollers, are just falling through the back gap as the grain backs up. All the grain goes though the top two rollers, there is no way for the grain to go around these. I have seriously restricted the throughput by cutting a 1.5 x 4 inch hole in a piece of cardboard and covering the screen in the hopper with this, and it takes much longer than the normal two/three minutes per bag of grain. This did not change the output, however. I think I will need to back out the mill gap. I will get a poorer crush on the grain that is currently going through fine, but at least gut SOME crush on the hard pale malt, and the biscuit.