OK so after reporting my findings to the asset owner, they had responded back and informed me that this is a known problem. Apparently the switches has an oil based cooling system integrated into them and it's this cooling liquid that is leaking.
I have exactly the same problem in one of our substations. Same droplets hanging from the middle bottom of the switches at the vent perforations. No signs of moisture ingress elsewhere in the panel or on top of the switches. The panels are vermin pro...