Can you post images to show what is happening ... or better yet, the solid part files?
Did you mate the inserted part?
I can't post files or pictures it's all proprietary data and I have redone the part so the error is not there anymore. Basically if you open up a solid .prt and make a block, then open another new part file and do Import-part, that gets to what I have. When I import I select the body, planes and axis and leave the body move dialog on. I locate the part using the datums from the new part and the imported planes. When it blows up the imported planes and the original planes stay where they are and the part is off in space 7 or 8 inches away. All of the machine cuts are located relative to the datum planes in the new part so they stay there. I have deleted the imported part and insert it again at the right location and the cuts all update... That's all I have....
is the cast part made inside of an assembly? could be one problem or you changed the cast parts location or how you built in the original and it probigated to the machined file.
show your solidbody folder, RM on the body icon, select save to a part file, name itXXX- machined and modify that body with the features for the machined one.
if the cast changes it will only change size, but if you modify feature like blind to midplane, yes things could go arye, like the cast part move from when you started the machined part.
takes some practice with this aproach.