Okay, since you did that research, I'll go into a little more detail, as much as is possible. Short answer is: I don't know why that error occurs. If you download practicalexample.j2l, for instance, that level does run in TSF. Some levels crash TSF, others don't, and I haven't yet figured out (read: bothered to figure out) what the distinguishing factor is. My guess is, once the technique becomes easy to implement, either here or through WebJCS, someone will figure it out without much difficulty and that will be that.

As for crazyanimstsf: shoot the flowers. They're destruct scenery, even though their initial frame is animated. You should have seen the same effect with the multi-color stomp blocks, although people tend not to notice those for some reason. There's another example in DryLava here which should also run in TSF.