Hi, New to the Forum. Need Help Please!!

Try a few bags of top quality bagged coal like Blashak. Stove size(lot larger) will not jam the grates.
How often are you shaking the grates? Sounds like a lot of unburned dropping down. I have exact same style grates in a furnace. Fact is once in a while you will get a jam from coal. I don't see it being the frame expanding or anything like that.
If you go to pea size you most likely will need to add more air under grates for enough burn.
Also with pea you can slow the burn way down .
I can remove my ash pan and actually see the culprit creating the jam on my handfired.
I take a poker and usually can knock it loose without disrupting the fire to the point of having to shut down.
Shaking with the short quick strokes as they said works the best

Thanks for all the help. I believe I may have fixed the problem. I took the grates and fire brick out and cleaned everything like you guys said. there was some build up on the backside of the fire brick which may have tightened my clearance up a bit. also in the pivots where the grates sit. used sand paper on them. Its been running for 3 hrs now and I can shake it!! I did lay a straight edge across grate and it does have some bow to it. about an 1/8 inch in center. Is this normal to have a little bit of bow in the grates? I will let you guys know if there is any more trouble. thanks again for all the help.

1/8th aint bad ..... If you start seeing 1" or more, that's a sign to change 'em out.

Glad to hear they're workin' for ya. Keep up with the ashpan daily, & you should get many years out of those grates.

The grates are cooled by the incoming air through the ashpan, up through the gaps in the grates.. As Smitty said, keep the ash pan emptied everyday, so the ashes don't get deep enough to restrict the air flow through the grates.. If the ashes get too deep, the grates will overheat and warp.

Cleaning out the firebox has a twofold reward: You now have freely moving grates, and you know how the grates and firebrick are assembled, and will be able to diagnose any possible future problems with the grates.

Greg L