Step and a reach. If the ball was within a step and reach to the fielder it’s interference. Sounds like that’s what it may have been but have to be there. If it was further than a step and reach and you go with obstruction then R2 is protected to third. Not past it.
With the exception that if multiple runners are stealing and the catcher is interfered with, but is still able to throw out one of the runners, the other runner could stay at the base he safely advanced to. The interference happened and was called, ignored, ball remains live and runner not thrown out advanced on the play. This would be the case in all rule sets.