On the CRR SD-40 as on the Sandpatch engines, if I blow the horn multiple times in sequence (such as blowing for a road crossing) the horn audio drops out and pressing the button or pulling the in-cab lever has no effect. Flying far enough away with the 8 cam then swapping back to the cab that a loading screen occurs while changing cameras, will fix the issue temporarily till it occurs again. Interestingly, this bug does not occur on the F7. I am running via steam on PC, Windows 7.
Update: I've only encountered this issue on clinchfield in the assent/decent senarios. Running services I've not encountered the issue yet.
Further update, just had the bug occur on one of the nora turn services. Made it through all of the other service set (forget what it's called) for the SD40 this morning with out it occuring. It took halfway into the 3rd part of Nora turn, where as in the senarios it took only the first 5 min.