The Fuji G690 / GL690 cameras with interchangeable lenses fire the shutter in the lens with a linkage using a lever in the mount. If you have the lens off you can see this lever move as you push the shutter button.
Due to years of use and possible wear in either the linkage or the lens mount, it is possible that the shutter might not fire at exactly the same time as the wind lock is released. There is an adjustment for the travel of the shutter-firing link, which is described in the service manual and relatively easy to access, so I assume it was something that could be adjusted during routine maintenance.
I described the link and showed photos in this thread:
https://www.photrio.com/forum/threads/fuji-g690-shutter-linkage-question.172654/#post-2251639 where I had a camera that sometimes did not fire the shutter at all. Unfortunately, nobody was able or willing to measure the intended travel of the shutter linkage, but I was able to adjust my camera so it worked. If you adjust the travel too far, then it interferes with the lens mounting (Fuji could have engineered that a little better). If you don't feel comfortable messing with it, then just remember to press the button fully.