I'm with Jerry on that too. The rams have a common oil supply, so there is no need to calibrate them. They are the same diameter so they exert the same amount of force to keep the arms moving at the same rate. That doesn't mean if they have different length rods in them that at full extension that they wouldn't try and twist the arms. Some rams have bits inside that limit the extension of the ram, i guess there is a possibility one has one and the other does not? Remote chance, but who knows.
I too suspect the weld point to be where the problem is, it may have stretched.
If the rods were different lengths on the rams, there is a possibility they are pulling more on one side than the other when fully lowered, but i didn't think they would have enough power to bend anything.