Drive Train Problem ERRR! Help!

I have a Nirve cruiser with a jackshaft assembly with an interplanetary Shimano 3 speed rear hub. I am not sure which is malfuntioning the hub or something to do with jackshaft assembly??? I had this hub since December and the same hub for over a year and have ridden this bike mostly on a daily basis. When the hub fially died I replaced the hub with the same hub which lasted only until about 2 weeks ago. The hub seized spinning the rear nut completely off, I retightened it only to happen 3 times.
I have since replaced the hub twice, first with a Sturmy Archer 5 speed and could not get it to gear properly under power but without the engine it worked normal.
I Bought another Shimano 3 speed like the one I was origially using thinking it was a bad hub.But same as the Sturmey Archer It also will not run under the power of the engine without skipping and throughing the chain off. Damn!
I can't seem to get it to function with either hub under power.
The Bike works great without the engine and go thru all gears without slippage. Once the engine is engaged it skips real bad, like its not all the way in gear??
I took apart the jackshaft assembly, checked all the gears, keyways and chains...
I am stumped.
Any suggestions I have had this bike for 2 years and never ran into such a problem. Its only been this past 2 weeks I have run into this. I tried 2 different hubs replaced by a local bike shop and have had no luck and the problem remains that the drive train won't work under the power of the engine. What am I missing?

Chain that is coming off is from the small gear to freewheel sprocket

I don't see how I can get to brand new hubs that are bad in a row? the freewhell has minimal play but it always has. The sprockets are aligned.

Thanks Ghost I have off tommorow and plan to tear the whole jackshaft assembly apart a realign the whole thin again.

I think possibly the jackshaft assembly needs some staightening but I ordered new housing from SBP and gonna have someone do it in stainless with a some extra strengh. The one I have now is 2 pieces, I had someone weld the right side and the part of the housing that goes bolts to the bike frame as one piece. That assembly has taken 2 years of straight cruising and 3 motors worth of abuse.. LOL: I was trying to rush this fix but think I I'll ltake the bike off the road for a week, sit back and examine it more before I make too many more moves.... This addictive hobby can become a money pit, and it's never been off the road for more than 3 days ( My daily commuter...work groceries etc. oh beer too) It can be a head ache but I love it!