Advice on AC condensation leak

Hi all,

I have had a problem for a while where my AC evaporator will leak condensation into the passenger footwell of my car, I have inspected and checked that both drain tubes are draining as the forums will often point out, but the problem still occurs. Weirdly this problem seems to occur at random, where sometimes the AC will run for ages without a drop, other times sections of the carpet will be soaked. Does anyone have any idea what’s going on?