I'm not sure if this is a bug or if it's been fixed but I find the dialog behavior I'm about to describe quite odd.
I've got a model in which I'm rolling back to an earlier feature and attempting to use Extract -> Region of Faces with Associativity turned OFF. I'm not interested in WAVE linking or associativity - I just want a single body with multiple faces and I don't want to have to use remove parameters (just a wasted step when I can turn off the Associative option).
So, I define the Region and when I uncheck the Associativity button, the Fix at Current Timestamp checkbox disappears. Then when I press OK I get a message that Fix at Current Timestamp needs to be turned on.
What gives - I can't turn it on. Shouldn't the default "logic" be that it's already ON whether it's shown or not? This isn't going to end up being a feature other than a Body so what does it matter where a dumb body sits in the Model Navigator????