don't run make update-po at all - you don't need it
Then should the following line be deleted from Makefile?
@echo "Type '$(MAKE) update-po' to update with newest strings"
And I still have troubles with "fuel".
Now it's missing "fuel tanks". Way to produce:
Install two fuel tanks. Wait some time.
Now you do save-load operation.
Check equipment of firebird. The left tank WILL BE (!!!!) installed for 2 hours. And right one simply dissapears!