"The third row has an "illegal" set of characters for YAWL... i.e. 3: <bracket><some number><bracket> <some text>"

Umm, yeah. We kind of needed to know that in the first place, since the data in your OP gives no hint that an illegal character creates the problem... and because it's just remotely possible that some of us who might offer (substantive) help might not be familiar with "YAWL."