'Measure numbers every system' should place numbers after split measures
If the first measure of a system is excluded - most commonly, when that measure is the end of a split measure that begins in the previous system - the 'Measure numbers every system' option simply skips that system. This is surprising behavior, as the standard practice I've seen in typeset music is to number the first normal measure of each system.
Attaching an 1800s folk tune which needs split measures for choral singing because none of the phrases starts on the downbeat. The result is that 'Measure numbers every system' doesn't place any measure numbers at all. Manually overriding the numbering achieves what one would expect 'Measure numbers every system' to do by itself, as in the second attachment.