Map labels fail with external check values

Steps to reproduce:

1. Recent upgrade to 4.2.1 from 3.4.x
2. Maps with dynamic labels showing external check values
3. Values now report *UNKNOWN* only in Map label
4. Items, Triggers, etc. all still functioning perfectly.

Result:

Expected:

The following Worked in 3.4:

{{HOST.HOST}:queryMiner[{HOST.CONN},ChipTemp,{$GOOD_BOARDS}].last(0)}

Now reports UNKNOWN

Oddly, calculated values based on the same underlying external check work perfectly, e.g.

{{HOST.HOST}:chiptempinf.last(0)}