I'm working on the Bronco 1:35 SU-152 April '43 boxing and I've noticed some short shots on some of the parts. What would be the best way to fix this short shot?

Those little triangular stubs on the bottom of the base? They might be locating stubs. Check the piece they are supposed to attach to to see if the receiving end has indents in a similar shape. But this is just pure speculation. I've never even seen the sprue shots of the kit.