Mine was a laugher. I paid $85 for a pool pro to come out. In the first 5 minutes he found the problem. This was over a year ago. With the suction plate on the end of the hose, it always raises the cuff of the hose just enough so that it is out of the water. But, for the first 10 years, this worked without causing suction to drop.
A slight, "break" - I won't even call it a crack - because it is far smaller than that - developed between the cuff and the hose. Even when I replaced the cuff with a new one, and glued it really well with the adhesive; apparently, it is tough to get a 100% airtight seal with the cuff and hose. AND... I actually bought a brand new hose from Leslie's. Same result! It would cause a lose of suction as well. This is what caused confusion and delays in me finding the source of the problem; believing the issue was not with the hose if the same loss of suction occurred with my old hose and old cuff, old hose with new cuff, and brand new hose!
Apparently, I was fortunate to have a hose with a 100% airtight cuff for many years, that eventually developed a slight air leak. The pool pro who found the problem, and he was the second pro, diagnosed it by removing and no longer using the suction skimmer plate, and instead removing the skimmer basket and hooking the hose directly in to the skimmer intake after filling the hose with water. Voila! The suction was strong and remained strong! The hose cuff was fully below the surface of the water; eliminating an entry way for air.
The downside to this method of not using the skimmer plate and removing the skimmer basket is that there is a small risk that I could suck a golf ball size piece of debris in to the plumbing with no skimmer basket protecting things, but, I don't have gumball trees and don't play golf. Plus, since I am manually vacuuming, I am always watching the bottom of the pool for what is sucked in to the vacuum head.
... Now, I have a Polaris 9300, and use it to vacuum the pool. But, I still retain my manual vacuum in case the pool gets trashed by a bad storm or if I need to clean the pool quickly.