Arc does not like Linear and Flip parameters

[bjlottis]

So I created what I thought would be a simple DB with one linear and flip parameter. I've attached the block for reference.

What's confusing me is everything seems fine when I first insert the block. But if I flip it first and then try to stretch the linear grip, the opposite end of arc stretches with the grip.

I'm not quite sure why this is, and how to fix it. I'm trying to avoid having to mirror the block half the time it gets inserted.

Thanks in advance for any help.

Brian