Project Oblique Mercator example b.mxb (Dropbox, 305MB) contains an image in a custom Oblique Mercator projection, using a rectified grid angle. The centre latitude and longitude are near the centre of the image, so some tiles have negative X and/or Y indexes.
Selecting tiles does not work correctly in this image. Ctrl-dragging in the left or lower part of the image is usually ineffective, and if a selection is made, it always appears in the upper right of the image instead.
The issue occurs in 18.104.22.168, 22.214.171.124 and 126.96.36.199.
Exporting (e.g. to TIFF) and reimporting resolves the issue. That also renumbers tiles, so that X and Y indexes begin at 0, but I don't know if that is relevant.
I've reduced the size of the image by replacing 3 in 4 tiles with plain grey, so it's ugly as well as still being quite large.