The design of having one hydraulic ram at one end (whether it's the heavy end or not, it's usually in the front) is completely normal. There is a shaft connecting the two gear packs keeping them turning at the same time. So, while it may look crazy, it's used all over the industry.
The washer trick is a band aid cure for a slide that is out of height adjustment. If the slide is adjusted correctly there should always be enough down force to keep the gear pack and the idler gears in mesh. The heads at the end of the idler tubes need to be adjusted down to increase the pressure on the idler tube while it is in motion going in and out. If Lippert advised anyone to do this, it's because they knew that telling them how to correctly adjust the slide would take time and if you don't do it correctly, you could throw things further out of adjustment.
What's causing the problem with your out of height adjustment scenario is, as the slide goes in, the weight of the slide is coming off the tubes too soon transferring to the floor of the RV. This is what's unloading the idler tubes and causing them to jump gears. If you look at the outside of your slide where your idler tubes meet the slide cross rail you will find the two adjustable heads. Each will have two bolts and nuts over slotted holes. The nuts/bolts lock them in place but when loosened can allow the head to slide up or down. Below the head is a long bolt with a set nut. This long bolt will raise or lower the head when it's set nut and the two previously mentioned nuts/bolts are loose.
Last summer my new rig had this very problem. When I brought it back to XLR to get it straightened out I talked extensively with one of Lippert's main techs who came to the plant to address my issue. He told me Lippert knows about the washer trick and they've also seen the gears cut off the bottom of the idler tube and welded on lower to try to scab a cure. None of this is correct. There is only one correct way and that is to align the slide in the trailer correctly. He said dealers, mobile techs, and do it yourselfers do this type of repair ALL the time but it just isn't the right way to do it and will likely lead to another failure in the future due to moving the stress to an area that it's not meant to be. He said he's always shocked that people go to such lengths to correct something but completely ignore the adjustments that are built into the system to cure this very issue...