eshopps 75g hang-on problems

[bigworm616]

i'm running an eshopps 75g hang-on skimmer on my 29gal. It doesn't seem to stay dialed in. I have taken it apart and cleaned the air intake to make sure it is clean. Following this it performs well, but within a few days it starts to produce less and less skimmate.

The system gets partial sunlight throughout the day, i'm unsure if this is contributing to my issue.

Are these skimmers known to have problems?

Any advice on how i can reliably calibrate my skimmer.