Well, I have to ask, did you check back with the pool shop that you bought it from?
In the meantime, there are a couple of ways of adjusting the water flow through the machine.
Both described in the manual.
The 1st is the restrictor plate on top of the machine. If the machine does not climb, removing it may help.
Next we have the "high velocity inlet". having this in place increases the velocity across the gap, so the suction is greater, but the volume of water is decreased.
So hard to predict if this will help. No harm in trying with it installed or not.
I have found that running the machine for 4 hours gives best results (rather than 2 lots of 2 hours).

No... it is best to keep it out of the pool and out of the sun, and whilst I don't do this every time myself, it is a good idea hose it out after use. Sun and Pool chemicals will affect the life of the machine -- it is plastic after all.
The arm on my machine did break off recently -- lucky it was still under warranty so they replaced it.
The other reason not to leave the machine too long in the pool is because you will be leaving the leaves which has collected under water also... this will cause phosphorous build up.
My machine is still keeping the pool very clean though -- so still happy with it.

Totally agree with everything Andrew said. Mine is 3y old and never had an issue. The reason to keep the caught leafs out of the water column extends to skimmer box and filter too. The smell often attributed to clorin, is really the smell of cloramin, i.e. the result of clorins action on the amino acids in leafs, rather clorin itself.