Are you using the v1.8 of the mod? If so, had you emptied the Save folder after activating the new version? The game runs a goodly portion of itself from data in the Save folder. That data will not "re-fresh" when you do a new mod configuration, unless you empty the folder and let the game re-create it.
Also, if there are only one or two escorts, that is sometimes "normal" behavior early war, where they attempt to put you off, aka: put the scare in you, by letting you know that they know you're out there - somewhere... not all of the escorts have sonar early, and that is usually the way they handle things, is to put themselves between you and the convoy, and attempt to "bait" you, so that they can hear you on the hydrophones. I don't think it is a purposeful thing on the programmer's part, it's just that the ship does not have all of the tools it needs, nor are there enough reinforcements to help sometimes. Next time you see that (or if you already know), get the escort type, and let us know which ship it is.
