SolidWorks Slot: Current entity is not valid for current mate type.



There is no way I can mate any of the objects on the guide to its slot. It's impossible. I spent the whole day yesterday and this morning, and it is just impossible. I removed all the mates, floated, fixed the objects, and tried all kinds of combinations, all unsuccessfully. Why?? Is it because of fillets on the guide? I did experience many issues near the objects with fillets applied.