I am running FreeCommander XE 2017, build 750 64-bit donor.
Steps to reproduce:
1. Open FreeCommander and go to any local drive.
2. Create an empty text file named ThisIsAnExample.txt.
3. Rename text file to THISIsAnExample.txt.
Error "File with the new name "THISIAnExample.txt" already exists!" occurs.

Note: I was previously running Windows 10 Anniversary Edition which worked just fine.