By Luc Olinga Rivian’s share price has fallen sharply, and after walking back an ill-advised price increase, the EV maker has a tough slog ahead. Everything seems to be going against Rivian (RIVN) – Get Rivian Automotive, Inc. Class A Report. Until recently the electric-vehicle manufacturer presented as a key challenger to the throne of Tesla (TSLA) – Get Tesla Inc Report. But two key stumbles — involving pricing and production — have severely clouded Rivian’s path forward. The first: an ill-advised effort to raise the prices of its vehicles, a move applied to customers who have already plac…