Title says it all. While reloading, crouching frequently interrupts a reload animation/process.
Suspect it may have something to do with having Toggle Sprint enabled. The logic of the movement engine may be ‘re-entering’ sprint enabled when standing occurs.
Have also occasionally had reloading interrupted while only tapping left/right/back, but near objects/walls, which may be causing elevation changes, and effects of that sort. Very hard to duplicate, but pronounced when it occurs (certain that this is a thing, because when you really want to reload, and have both Sprint Cancels Reload/Sprint Toggle, you avoid the forward button like it’s cancer in those moments).