I am running Photo Mechanic version 5, build 19749 on MacOS Mojave 10.14.6
Files from Canon 1DX Mark III. Initial filename is AX0I0002.CR3 etc
Renaming string: BOYKO_200422_{fnum}
Files are renamed correctly: AX0I0020.CR3 becomes BOYKO_200422_0020.CR3 and so on, however every file that I had color rated in Photo Mechanic was renamed incorrectly and AX0I0004.CR3 became BOYKO_200422_4.CR3, file AX0I0086.CR3 became BOYKO_200422_86.CR3 - the number are not in 4-digit format anymore.
I understand my ability to use {filenamebase:-4} var, but will appreciate if the {fnum} issue is fixed.