Interference?

If that was my runner and he was called out I would be upset and I would have a conversation with the umpire.  IMO no interference or even a case for interference at all. That is....if I am reading your post correctly.

My 2017 son recently informed me that he has deliberately slowed down A BIT between 1b and 2B or 2B and 3B to obscure a fielder's ability to see and react to the ball if they are playing deep. If it is obvious, he won't do it, but if a little hesitation and jumping out of the way of the ball can help, he's done it, but maybe 1-2 times per season (tops). As far as I know, he's never gotten called call on interference for doing it.

If R1 was running normally, and if R1's path didn't cause F4 to "pull up", then it's legal.

(And sometimes it's hard to tell if R1 caused F4 to pull up, or if F4 just chose to stop charging the ball.  the higher you go, the more you're going to expect F4 to "play normally" and force the interference call -- if it's there)