Actually all versions of B4A use the optimized dexer by default and fail to the standard dexer in cases of errors.
The single purpose of the optimized dexer is to reduce the compilation time. It does that by processing the libraries in the background and then waiting for your code to be processed. If it fails then the solution in most cases is to increase MaxRamForDex to a higher value. The issue is probably related to Google Play Services which is a large library.