Retina 5K, 27-inch, 2019 / OS 14.4.1 / Illustrator version 29.8.1

This looks like a new visual bug. There seems to be a problem with the way Illustrator is displaying clipping masks. It has only started happening recently.

The attached image is taken from a file that worked fine before.

The wavy lines are contained inside a clipping mask (the same shape as the blue section). I have included images of the lines outside of the clipping mask (above) and inside the clipping mask (below).

Any separate objects placed behind this clipping mask have a section missing (see black shape behind). The clipping mask and the black shape are completely separate. The black shape is just a rectangle.

This only happens with clipping masks that had been created in the past. Any newly created clipping masks do not have the same problem. However this is quite a big problem for us as we have hundreds of files, each with multiple clipping masks. It won't be possible to recreate them all.

This is only a display issue. Any exported images don't have the missing sections.

Note: this only happens when in View using GPU mode. When I switch to View using CPU the image displays correctly.