In the following post you could find more details about DEM creation,
I have similar machine it works well for me, However I’m intending to increase the RAM to 32 GB,
Is still this the case? IF yes, might be you missed the update of your SNAP and it affects, from the Help tab you could check up for updating, in case it does’t work remove the SNAP, and reinstall it once more,
I agree totally with our colleague @ABraun that VV polarization is the best option and it gives better coherence, I checked up this also from my personal experience, But you said
It’s not mistake, I think you could apply both to disclose the differences yourself.