Are you trying to load different images to the same sprite frame?
If you want multiple instances with different images you have to add multiple frames to the specific sprite, then change to a different frame when loading.
Just setting a private variable wont help unless you do something like compare private variable-> set frame
BTW sprite has a function for this already "Load animation frame from file".
I try it and I have found a Construct BUG!
If you go to debug mode, press enter and after space, Construct crash!
the critical code is: