This may seem trivial, but the flap covering the mirror on the driver's side visor has loosened a bit, so that now it is not completely closed when the visor is in the down position. (especially if pushed forward a bit) So far it only gaps about 1/16 inch, but I and concerned it may loosen further with time.
Is there a way to tighten the spring or whatever holds it closed, or is replacement the answer? Also, would this be a warranty item?
Thanks for any help.

 

Depending on how old your RX is, this should be covered under your warranty. Suggest a visit to your dealer, they will likely order/install a new visor.