Error message when renaming files

Hello,
I am encountering an error message when renaming files.
Currently, I have 31 files named:
01-05-2026 Sportsingel up to 31-05-2026 Sportsingel.

The intention is to rename these to June, for example:
Old name: 01-05-2026 Sportsingel
New name: 01-06-2026 Sportsingel.

However, when renaming, the date is not updated in sequence. The file name is duplicated instead (for example: 01-06-2026 Sportsingel 01-06-2026 Sportsingel), which results in an error message.

The expected result should be:
01-06-2026 Sportsingel
02-06-2026 Sportsingel
03-06-2026 Sportsingel
and so on.

Could you please advise what I can do to resolve this issue?

I hope my explanation is clear. If you require any additional information, please let me know.
Thank you in advance for your assistance.

Kind regards,
Mark