Few weeks ago I think I got this situation when two convoys passed not far away from each other. It happened just south of Iceland. Hydrophone guy picked up several contacts with different reports. Some of merchants were closing, some of them were moving away, however all those contacts were comming from about the same bearing. The situation was confusing. First I thought perhaps the convoy is changing course ? But some time later I noticed the common convoy group noises are splitting up - one was heading east, while another dead south, both were moving away from me. I chose to follow the one that headed eastwards.