Tags with accent are not displayed correctly

Hello

I am French so my tags may contain accented letters. But accented letters are displayed with a “?” in a diamond.
Ex:

When I look at Metadata, sometimes accented letters are correctly displayed but not always:

But when I use another tool (XnView MP) to watch Metadata on the same image, I don’t have this issue:


Do you know any settings to fix that ?
Is it a bug I should report on https://bugs.kde.org ?

Thanks for your help

My Digikam version: 8.6.0