Thumbnail filenames appear fine when the text is in no way selected.
When a thumbnail's filename is selected in whole, it appears legibly but narrower than when not selected and, if the name is short enough to, when selected, not fill the full width of the filename area, the non-selected name still shows beyond the right edge of the selected text. Kinda weird.
If the thumbnail's filename text is selected not in full, but just a range of text is selected, that selected text is clearly visible but the rest of the file name appears on top of the still-visible underlying filename such that it, such that the non-selected text and the underlying filename are jumbled and unreadable.
And if the filename is selected but the insertion point, only, is anywhere in the filename (including at either end), the entire filename is unreadable except for any of the underlying filename that might be still visible beyond the selected filename.
I've attached an image showing the four states detailed above.
Macintosh Studio M3 Ultra, 512 GB RAM, macOS Tahoe 26.3.1
Photo Mechanic Version 6.0, build 7285 (fb3e520)
Thanks, Mark