Beamforming - FK Analysis

Hi, I am using Beamforming/FK analysis as per: Beamforming - FK Analysis — ObsPy 1.4.0 documentation

I am working with very high frequency data (order of 10kHZ) and getting unreliable results (azimuth/slowness change significantly when slightly changing paramters)
and I am wondering if there is an optimal set of parameters to feed ‘kwargs’. i.e. is there an optimal window length/ step fraction etc. for this purpose?
Thanks in advance!