I'm not sure whether it's a glitch or I'm overlooking something.
I have an attribute (activePage.Sequence), defined as an Integer.
The image filenames all are in the format yyyymmdd_hhmmss_x.ext
My custom sort profile is 1) activePage.Sequence (asc) and 2) File Name (asc).

Sorting always worked fine, but recently (currently working with version 2021.16.4) the sort is not correct anymore. Applying the custom sort profile shows images with a high Sequence number, in the midst
In the file window attached, the filename is on top (yellow) and the activePage.Sequence is below the image (white text)

ger