reported earlier Bug - Changing a Group's County can inadvertently and wrongly change many Unit's Types.

[cfrag]

If you assemble a complex group of ground units (for example set up a SAM site) that contains different Categories (for example 'Unarmed' for the resupply trucks and "Air Defence" for the Launchers and Radar), changing the Country (say, from "Combined Joint Task Forces Red" to "Combined Joint Task Forces Blue") will incorrectly change the group so that ALL UNITS NOW ARE FORCED TO THE CATEGORY OF THE FIRST UNIT. This will, for example, result in changing the resupply truck (cat Unarmed) to a FLAK 8.8 cm (cat Air Defence) if the first unit in the group is an Air Defence unit. 

People unaware of this, and who are changing the country of large, complex groups will often not see this change, and can ruin a lot of effort with a single click that should not result in these highly impactful changes.

It is 100% reproducible.

[Flappie]

This got reported last year.