Blueprint implementable function crashing when called from c++

The crash is happening not inside my code , but inside the unreal generated caode that calls the function .

Function itself as defined in c++ base class called AC_Waypoints

UFUNCTION(BlueprintImplementableEvent, BlueprintCallable)
FVector mfo_bp_NewGetNxtWayPoint(UC_LoopCounter* in_pWayPointCounter);

The function is implemented in blueprint

But when i run in debug mode from VS , it crashes in the function below, which is part of the generated code

static FName NAME_AC_Waypoints_mfo_bp_NewGetNxtWayPoint = FName(TEXT("mfo_bp_NewGetNxtWayPoint"));
	FVector AC_Waypoints::mfo_bp_NewGetNxtWayPoint(UC_LoopCounter* in_pWayPointCounter)
		C_Waypoints_eventmfo_bp_NewGetNxtWayPoint_Parms Parms;
		return Parms.ReturnValue;

The the function genrates exception on line ProcessEvent(FindFunctionChecked.
The exceptions says access violation.

I have used blueprint implementable functions in the past so not new to using them, but i suspect maybe something about my project is corrupted causing this problem.

I have also deleted all other files in project to regenerate new c++ project , but this changed nothing .

I added other functions of same blueprint function event and got same exception.
Started brand new project added blueprint function event and that worked fine. Thats why i suspect its something to do with corrupt project.

Any help much appreciated. Thanks