My Tuscany 2015 is quite similar to the ARIA. I had similar problems with
the single handle faucet too. I found improvement by adjusting the screws
near both the hot and cold lines going into the mixing chamber. Get access by removing the face plate from the faucet handle. Yes your dealer may be correct. On the Tuscany I would have to remove the stackable dryer and access the plumbing from the dryer side. Maybe the washer too?
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