This is not only a THOR problem. Most all RV manufacturers use the same systems and I have heard of horror stories, especially of the super slides, from Winnebago and others.
I don't know what percentage of slides fail but I suspect it is a relatively small number...it's just we only hear of the ones that do. I do also suspect that of the failures, most are with the super slides due to the weight of the slide.
Do some reading and you will discover that every slide system has its risks and failures. It's just we don't hear of the vast majority that have no problems. I have two slides with NO problems.