Found the problem (potentially). The two coins on the right side of level 1-5 have the wrong variables attached to them.
If you get the one on the left last it should fix it. Let me know if that solves the problem. Thanks for sharing the bug!
Thanks for checking in on it! Unfortunately, my star count is still stuck at 16 (and to answer your previous question, I can't unlock the "17"). I believe I got the one on the left last during my first run through as well, but I tried again just in case.
Dang, thought I had it there. Okay, thanks for checking. Could be more of the same bug in other levels perhaps. I'll have to go snooping amongst the code some more. Thanks for the help!