Error "File already exist" when Change case of file name Unicode

I have some files music with name Unicode
Original name - Vietnamese

name in "Unicode C string encode" - "English"

1. "\x43\x1EA3m \x1A0n" - "Thanks"
2. "\x43\x103n Ph\xF2ng" - "The Room"
3. "\x43on \x110\x1B0\x1EDDng M\xE0u \x58\x61nh" - "The Green Road"

I want upcase all character, so I use methose "Set upper Case", but AR has error status: "File already Exist"

Error:
if in new filename : Only change case ASCII character ==> AR status: OK
If in new filename : change case of other Unicode character (example: ==> AR status: "File already exist"


Please fix this. Thank you very much.

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