Recoded "con9a" to make invalid units missing, fixes #173
Recoded "con8a" to make invalid units missing, fixes #172
Recoded "con7a" to make invalid units missing, fixes #171
Recoded "con6a" to make invalid units missing, fixes #170
Recoded "con5a" to make invalid units missing, fixes #169
Recoded "con4a" to make invalid units missing, fixes #168