I just finished a highly successful patrol (Palau-Rabaul, Dec 42/Jan 43, 5 merchants sunk) and was awarded a medal and then offered the choice of a new submarine or to continue with my current boat. Fortunately I had saved just prior to docking, here's why;
I took the offer of a new boat. I had over 3000 renown. My SD Radar and SJ Radar slots were now both empty (given it was a new, up to date boat you'd think this would have been automatically installed). So, I 'purchase' the SD and slide it into place, then, with plenty of 'renown' remaining I 'purchase' the SJ-1 radar but can I slide it into place?????.........Nope! A pop-up tells me I'm not allowed to do that. Needless to say I was torqued.
So I reloaded my saved game, arrived in port, picked up my medal and when offered a new boat told them to go pound salt and stuck with my old boat which already had the SD and SJ I'd acquired previously. I grabbed a couple of the wee homing torpedoes and set sail on a new mission.
I know this issue is not related to the mods. Can I suggest a mod that automatically gives every (appropriate) submarine the 'extra' toys based on the period of the war and NOT this stupid renown system??
OK, done venting.