presented the following explanation :
https://www.screwfix.com/p/lap-led-f...daylight/665cc

You can see the cable entry gland... I have my LED floods pointing downwards
to avoid annoying the neighbours but that makes the cable gland face the
rains from heaven!

Have you used a suitable sized round section flex, to allow the gland
to properly seal against it? Did you grease the gland seal to stop
ingress?

For a fitting outdoors, I always advise to do your best to prevent rain
getting in, but to drill a hole in the base of a unit, to ensure any
which does get in can drain out. Though I doubt this would be possible
with these fittings.