it’s not really a map chip issue – unless your Navionics chip is unlocked. make sure that little slider on the chip is in the locked position so nothing can write to it. locked map chips aren’t involved in waypoints or screen captures (unless you confuse your unit with an unlocked chip). however, it could be a blank SD card issue…
my guess at the cause is that it’s trying to save the screen capture image to an SD card first, and then the process is hanging up at that point because there’s no blank card present, so it never finishes the waypoint save on the unit itself.
try inserting a blank SD card into the left slot with your map chip in the right slot. then hit “Mark” and see what happens. it should save the screen capture to your SD card and the waypoint to your unit.
or without an SD card in and just your map chip in the right slot, try turning off the screen capture feature and then hitting “Mark,” it should save only a waypoint to your unit.
last, but not least, make sure all of your networked units are running the most current versions of the software that’s available.