Stagger on two alternating tracks - Bug?

Alright, here it is:

As you can see, I tried with three different sets of files. In the second one I tried, it actually worked as expected. I’ve tried with other file sets now as well, it’s like 50/50 or something. Seemed to be linked with file naming (like “number” - “name”) but then that didn’t work with another file set so that wasn’t it.