Win 11/ Steam
I noticed this error only once
With Haudenoshawnee I shipped the “New Ways” card
then I selected the “Cavalry Cuirass” upgrade to increase hitpoints.
When the upgrade finished, the cavalry’s hitpoints were boosted by nominal amount, like they were supposed to,
but then I sent a shipment of kanya riders and the upgrade the hitpoint upgrade dissappeared and hitpoints was reduced to pre-upgrade level.