Hi,
I faced the same problem since A couple of weeks ago and I still have a support case opened to fix it (apparently it’s a bug), the only workaround that I have found is to ensure that the picking is done from only one location. This can be done by unchecking the “allow split” option on all my location directives, then if a product quantity is not enough to fill my work line from only one location, I will get a work line with location in blank and I will know that I have to make an inventory movement in order to have inventory to make only one pick. Hope it helps.