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The position of the feed to the shower shouldn't matter. Have you checked for debris in the hose assembly?
Maybe take the shower hose off, and then turn the water on and direct the pressure to the shower. USE A TOWEL so it doesn't spray everywhere and check for obstructions. These things are plastic and debris can get into them during the manufacturing process.
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2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.