Check out mudhouse(Sherri,s)web page. It will give you alot of help.

I spent some bonding time with my doors today and found at least one major issue. The wheels on the top keep comming off. Not off track, off the door itself. Looks like they just pop of and on? How can I secure them so they stay? OR should I get differant ones. All four of the top wheels keep doing it and allowing the top to come off track. This unsteadyness causes the door to jam.
It seems also the top track keeps sagging and the bottom track comes up also jamming the doors. I just assembled the top onto the base and set into the ground, no 4x4s so the bottom bends on the base easily. Ugh...

Hi Willa,
To work well, the top and bottom tracks need to be parallel and solid. I do have a wooden base under the steel GH base, and that might provide some stiffness to the bottom track.

One idea is adding an extra brace to the frame right over the top of the doors, to stiffen up the top track. That seems to help the doors operate more smoothly too. We just added a piece of oak we had, but others folks have used a piece of EMT or aluminum angle in the same spot. The idea is to help prevent the top track from sagging at all if possible. (click to enlarge)
{{gwi:297777}}

Also, this is a good thing to check...there's a small illustration at the bottom of page 15 of the manual, labelled Side View. (Shown below.) This shows you that the small black plastic clip Part 51 has to be guided onto the bottom door track so the small vertical part of the aluminum track is actually threaded up into the vertical gap in the center of black plastic part 51. If you do it right, the bottom leg of the black plastic "L shape" goes down the front and under the L-shaped aluminum door track, as the illustration shows.
{{gwi:288756}}

If you don't install it just like the manual shows, it's actually possible to install the doors so that the black plastic part 51 is just sitting on top of the door track, sliding along in the small valley there. Although your doors can function (sort of) this way, they can also fall off, since they're not truly captured at the bottom in the manner the kit intends.

My doors can't even be pulled off the track, top or bottom. I've honestly never seen anyone comment that the wheels can be pulled off the door itself, and there really shouldn't be that kind of pressure on the door to cause that at all...it makes me think something else is wrong with your door tracks (problem with your bottom track rising up?) or, with the black clip not being installed quite right, as in the illustration above. I'm kind of scratching my head over what would possibly cause that. :-(

This part of my blog talks more about the doors, in case there's anything helpful here to you: Assembling the roof, windows, and doors

I recently went through a door modification to my 10x12 after a blow out. I hadn't secured the roof windows enough and the wind got in the HFGH.

Here's what I did
{{gwi:297780}}HFGH Greenhouse Door Modifications

Well, I had the emt pipe, 2 boxes of screws and plans to remod the house when along comes a storm while I was on vacation.Sense the wind has managed to disasemble the gh for me, I now have ample oppartunity to fix and repair any issues with the gh. Wind took out all but 3 panels, two vents are mangled, ripped apart the door beam and the roof supports on front tipping the whole roof to the rear some. Heck I might even weatherstrip now. Gotta order new clips though, who knows where they ended up. All my panels got stuck in the fence thats on the sides so they didnt go to far. I will do a count tomorrow to make sure. My mom who was petsitting gathered them up for me luckly.
Ugh, Thats what I get for putting it off. At least its not a loss, just a repair and reinstall. (without using the directions LOL!!)

Willa