Roblox falls after Bleecker Street Research discloses short position

** Roblox RBLX.N shares fall 2.76% to $52.87 in early trading

** Bleecker Street Research says it has taken short position in the gaming platform

** Adds that child-safety overhaul, including mandatory facial age checks, brought little safety but hurt RBLX new users growth

** Says it bought 100 age-verified child accounts for $190.91 and logged into all of them from five countries in 2 hours without RBLX asking it to verify again

** Reuters could not independently verify the claims

** RBLX did not immediately respond to Reuters' request for comment

** Up to last close, RBLX down about 33% YTD