we've had those sounds, off and on, at various times, but usually when in very hot months. I've always assumed that it was the chassis 'settling', or even expanding/contracting, or something similar, but have yet to see any change in the leveling legs during that time - I would not think that's what it is.
I've crawled under the chassis, during these times of sounds, and still could not 'put my finger' on what was actually making the noises, though they seem quite loud at moments.
Most of the year, I never hear anything... so it certainly seems to be temperature related, at least for me.
I've also never sprayed or wiped down my legs with anything - and they've performed flawlessly for over 4 years and many, many extractions and retractions, over 85,000+ miles and many off-grid parking nights.
It seems if the legs had any issues with the hydraulics, they would only lose some height very slowly, not in pops or pows, and the loss would start to become noticeable as you would also be becoming 'unlevel' within the coach.
also, if you drop you air bags before you level, your legs will have less height to maintain, and you'll be on more of a stable, and lower 'foundation'.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada.... formerly Georgia, then NorthCarolina, now Alabama : )