SW 2014 SP5

I have an existing drawing and want to group some rev symbols so they stay with their dimension. I was able to get a few to group, but for some reason don't have the option with others. Basic dimensions, and just your normal rev triangle. I cant tell any difference between the pairs that will group, and those that will not.

I tried laying down some new dimensions and grouping with those, but no luck. What am I missing? Possible glitch since the DWG was made in 09?

I did start a new drawing to experiment, and am able to group with that.