Product and version: FileMaker Pro 126.96.36.1993
OS and version: Mac OS X 10.11.6
Hardware: MacBook Pro (Retina, 15-inch, Mid 2015)
When selecting a group of objects on a locked panel or locked graphic object such as rectangle it is easier to select the group by dragging. This will select one or more items which are not wanted in the group ( usually the panel ) but they can easily be deselected by shift-clicking. However, when applying an alignment ( typically left align ) the group aligns to the left of the window instead of aligning to the leftmost item.
How to replicate
Place several objects onto a locked tab panel, slide panel or rectangular object. Select the objects by dragging from a point outside the panel until the panel and the objects are selected. Shift click to deselect the panel. Align the objects to the left. The objects will align to the left hand side of the window.
Workaround (if any)
Without modifying the selection, undo the last action and then repeat it. This time the alignment command works correctly.