This is a common issue with the RTA stuff and probably one of the reasons it's so cheap. I've owned two of these Producer Stations and have found that the biggest problem with them is that they are very, very particular about precise alignment during assembly. The trouble is that they allow no 'wiggle room' at all between rack units, so there is no room at all for mis-alignment. This is particularly problematic with gear like rack-mounted CD players or some of the old Roland MKS units that have a sort of 'lip' extending from the front panel. Ditto for MOTU gear which has screwed on rack ears that are not always perfectly parallel to the front panel. Also, some of the rack rails are sometimes not at perfect right angles to the tubular supports. Again, because there is no wiggle room, this can put the rails out of alignment.
I've made it a practice to install rack panels or expendable rack gear into them when assembling them to help keep things lined up as best as possible, but it's never perfect. I also find that I sometimes have to slightly unscrew every piece above or below a space into which I am inserting a new piece of equipment to make sure it all fits, and then tightening it all down again once I have it aligned. Definitely a case of getting what we paid for - and little else!