I hate it! Autodesk should work on this problem!
Booleans suddenly don´t work when Geomitry is too Tricky!
I had the same problem and I asked in a similiar thread about that topic, and everybody get lost when they road booleans!
Try to booleans 2 cubes in your frog scene and you will see that it works, but on your frog not.

I hope that anybody else can help you, but I don´t think so!

Probably you must remodel everything and do booleans a part bevor!

Sorry...