What triggers new sub promotion

[Captain Joe]

I played SH5's Total Germany mission through once before 1.2 and I was given a promotion to a new sub v11c and when 1.2 came out I restarted it and finnished it but with no promotion. Was wandering what triggered the promotion of as I did all items that were asked on both occasions. Is there any mod that could have disabbled this or could it be 1.2 or have i forgotten something?

[Karasunx]

The same thing happened to me but in reverse. The first time no new sub, and the second time I got an upgrade. I think it might have to do with renown earned because my second time through I sank a lot more tonnage before returning to port.