Thanks everyone for the explanations. In particular, the part I did not expect was: English Channel tapping Picardy does not stop Picardy from tapping Brest. Regarding backstabbr, apologies for the inaccuracy, but it appears that when I ensure all units actually belong to the correct country, then b...

We ran into this situation, which didn't resolve as I expected: https://i.imgur.com/82Swpxz.png England (pink)'s orders: The army at Gascony move to Paris. (fail) The fleet at English Channel move to Picardy. (fail) The army at Marseilles move to Burgundy. (fail) The army at Brest support move to Pa...