.Net Application crashes without exception when calling unmanaged Api. Dump indicated Exception 0XE06D7363

I have a C#.Net application (.Net 4.6) which is using unmanaged Api developed in c++. All was fine for months; however since last week application is silently crashing when first method of the Api is called. There is no exception thrown. No exception is found in EventViewer as well.

I used DebugDiag to generate crash dump. The dump file name indicated 'First chance exception 0XE06D7363'. Tried running crash analysis on the dump; however, that didn't work either.

What could be the issue? What else shall I investigate?