Hi Zuzana,
just changing the path in the project file did not help.
However, it made me think and I checked the new folder - it had only a few KB. So I looked and the sfm2.dat and the controlpoints0.dat were both missing in the new folder. Once I copied those into the new folder, it worked.
So what happened is basically that RC kept the older file path and all the changes must have been saved there.