Kilosort4 is much slower when run from Spikeinterface than from Kilosort 4 GUI

Hi all,
I have seen others mention this, but have not been able to find the solution.
When we sort a neuropixels recording with Kilosort 4 using run_sorter (default settings, but with delete_recording_dat = False) processing takes about 6 hours, but when we use the Kilosort 4 GUI (same settings) processing takes only about 2 hours. Why is this?

I believe that the GPU is used for processing: we had a faulty installation previously and CPU-based sorting takes about 4 days with the spikeinterface-based scripts. The difference in duration is striking nonetheless.
Is there anything I need to change in our functions (see attached) to make them perform 'normally' (like the GUI)?

I've tested if saving the preprocessed data (tem_wh.dat) helps speed things up, but this doesn't seem to make a difference.

Our system is:
HP Elite Tower 800 with Windows 11 pro
96GB RAM
GPU: Nvidia RTX 4000 Quadro
We generally run the our scripts from within an anaconda prompt.

clusterKSort_NPX.py