From the right side of a selection, I can both “trim” and “trim slip”, and it works correctly.

However, from the left side of a selection, I cannot “trim” without it also moving the media.

I need to move the “cutout” media one frame, but I can’t do this unless I overlap the clips by dragging the entire clip. But this is not a solution.

All I need to do is trim from the left, but if I try, it instead performs a “trim slip”. When I try the “trim slip from the left” it performs a “trim slip” just the same as when I try to perform a “trim”.

Here is an image, but I don’t think it can really explain why the “trim” function doesn’t work.