Loose tracer rounds when placed in the vicinity window look exactly the same as normal rounds due to the lack of the star symbol, as a result you instinctively drag them onto other rounds that are in your inventory to combine them, but they actually get swapped because they are different ammo.
Obviously this is a very minor inconvenience, but still annoying nonetheless.

P.S. Please just make it so ammo automatically combines when picking it up, it would be such a huge QoL feature. <3