Breaking a siege by landing into the harbor no longer available?

[MrFreeze]

In others PI games I used to break an enemy siege of a coastal province by directly transporting the army by boats to the city, it doesn't seem to work anymore:

Me (Spain) helping my friend (France) who has a city (Bastia-Corsica) under siege by our commune ennemy (England). I sent my transport ships to Bastia with 10k men, when they arrived they didn't fight the english troops, I had to move them outside the province, in Ajaccio, then send them back in Bastia to attack the english. Can't we attack directly by landing anymore?

 

[James_Manring]

I think it is a problem with units detecting when they should be in combat. Sometimes I saw units behaving this way in my war with Portugal as Spain and they did not come from a transport.