I can't change the dimension directly, but if you window select all the features on one side, you can use the steering wheel to move them, and the 30 dimension changes.
We can set aside for the moment that you didn't make it an assembly, and you didn't make it sheet metal, and you didn't make it multibody. I'm sure that's an interesting story on it's own.
Sketch1 has a locked 28.75 dimension. If you unlock that, you can change the 30 dim. Does that work for you?
I can go into the why I did the model this way but after I figure this out.
I don't understand why a sketch affects the model but I deleted all the sketches. Then I could change the dimension in increasing numbers. Then I tried reducing it to 27.00 and now it's locked again. I can't change it in either direction now.
Help me if you can I'm feeling down...
Anyway, Matt, in ordered this was set up to be a simple x,y,z dim variable table driven part. And it worked. I don't want the user to have to do steering wheel driven mods. I've converted a few others to sync with success but this one is a problem child.
As to why they are modeled this way is because we don't detail these parts as sheet metal or anything else. They are basically assembly place holders for size and position. The shop builds them to size from standards. So we want a simple representative model without the useless overhead of sheet metal assemblies and we want the lines they generate on drafts to be minimal.
OK. I think I got it to work. It was one teeny dimension missing which apparently caused the software to be unsure what to do with that area and become filled with self doubt. Naturally the errors and balking contained no clue as to where the problem might be. I just have to watch carefully and minutely at area(s) that don't change as expected, then constrain it with dims or relations. I can't really blame the software but it would be awesome if it could narrow things down for you.
You might find that the "less is more" approach is better when it comes to controlling synchronous models with dimensions. Don't fall into the "fully constrained" history-based trap.
Also be careful of things like fillets. There was an edge in your model that had a round on it that consumed a face and might have prevented some edits. Rounds work best in ordered.
I dimensioned the hell out of it trying to find the problem. After I found it I reduced dimensions that had a symmetric twin. I wish that sync did have a conflicting relation warning system which could be based on current live rule settings.
It did have to do with the rounds. I had to add a dimension and a concentric relation. It works but I may add them in ordered instead.
Unfortunately with sync right now all it gives is an error pointing to the very dimension you're trying to change rather than to features that are causing the software confusion and need constraining. I know that automatic iterative trouble-shooting is hard but...