My Hi-Lo stutters when lifting
 

When I push the button to lift the trailer top, the whole thing stutters as it goes up. I mean, it shakes.

It does go up, but it stutters. That's the only word I can think of.

Any idea what might be causing this?

It slides down perfectly well...

First I would check the high pressure line for leaks
With the top down the fluid should be at the top mark
Are you leaking fluid out of the lifting ram?
If you are you may have to replace the seals
Hope this helps

Those guide blocks may need a lube job. I lightly lube the guide rails with grease then wipe them down, so there is only a very light film of grease. top is down when traveling, so no road dirt. It may also be, the unit isn't level, front to rear, and one side of the blocks are rubbing on the rails.
Tree

Make sure the side rails and the guide blocks are engaged properly. The lubing, as mentioned, is a normal maintenance operation. You can also try rubbing the rails with paraffin in the front surface and into the side grooves. I used it regularly and it worked very well and didn't leave any mess. I believe it was suggested by the boys at JR Repair.

I use an old candle and rub and wax the guide rods. Works for me.
Beach

That's a great use for those old candles. I never thought of that.:)

Don't use the wife's Yankee Candles! She will pitch a fit. Don't ask me how I know!! :D

Bob

Raising up the HiLo.
 

When we raise up our HiLo I always say it shimmies some like it is dancing. Never perceived it as a problem.

I forgot to mention if the trailer isn't reasonably leveled you can get jumping, skipping, etc. It can place undue stress on the guide blocks.

If it's level and the guide blocks are not grabbing, you might check underneath to make sure the cables are all on the pulleys properly. There are a lot of pulleys under there, as well as the ones right in the top of the bottom section sides. I would think a cable off a pulley would make more than a little shaking, but it might be good to check.
Roger