Differences in NIOS versions 11 to 12

I am new to the NIOS development so please bear with me.

I have inherited a legacy product (over a megabyte of source) where the former developer is not available for consultation.

The software system compiles without error in both NIOS versions 11SP1 and 12. The binary from the version 11 compiler operates correctly and has been successfully in the field for at least a year. Recompiling with version 12(also 13 I think) causes a failure in what appears as a keyboard repeat function.

Under version 11 holding a key down long enough causes the desired repeat function, under version 12 the repeat function never times out and the repeat never happens. I am attempting to determine the source of the timing for the repeat function but haven't determined the origination yet.

I realize this is VERY thin information, but I was hoping there was some general information concerning the differences between the versions that would help me get a thread on my problem. The source is very convoluted, non commented, and totally non structured (I know, whats new?).