Which version of SolidWorks your're using?
Try to move to the latest version or change to other PC, this problems happened with me some time and when I upgrade for example to the latest SP version the problem disappear.
Am using solid works 2017 SP 1.0
I also tried to open the same assembly in another PC, same problem exist even there.
In SW 2017 to make bottom-up links working first open part-in-assembly, open equation manager and then update equations (links).