All I can offer at this point is that the 2018 software functions differently than the 2017 software.  It looks broken to me, but it could just be they want it entered a different way.  I entered the same info in 2018 and 2017 and got a completely different result.

This is the first we've heard of it in the community so it might not be a known bug.  You may need to call support to report it.

There's an "Ask me anything" going on, so you might also try asking there.

Rick