Isolation Level Conflict

Hi i was asked to look at a third party app recently. There were a few queries doing giant reads and that was easy enough to fix. However, while i was working on the queries i kept seeing different transaction isolation levels being set. I've not really seen that before. I also was looking at the wait stats and LCK_M_IX is at the top. Did some reading and that can be caused by incompatible mode on another thread. My question is: is this happening because of the queries setting different ISOLATION LEVELS? I'm seeing repeatable read quite a lot. And Serialisable. And read uncommitted. And the database isolation level is read committed snapshot. And the developer has proposed adding more specific isolation levels in their c# code to fix it. I thought that might well make it worse! Which is why I'm asking the question.