My Equal-i-zer did the same. The hitch shaft in your receiver has some slop in it. It's just enough that it causes the head to rock a little. The first side you put on will pull the hitch down, making it fairly easy to put the bar on that side. It's now under tension and pulling downward. The other side is now higher. But the bar on the other side has to be lifted higher and with more force to get on.
Once on and the fact is raised, both sides are the same.
Tip...raise the tongue attached to the toe vehicle higher up, to where there is no tension at all on either side. The higher up the tongue, the easier the bars lift up. No need for the cheater at all.
I raised mine high enough I would lift the bars on the L bracket with the toe of my foot
Again, it may seem like it is unequal tension, that's because of the rocking due to slop in the receiver shaft.
Keep the L brackets the same length or you will have only one bar bearing the entire load.