Another obstruction call

[CecilOne]

Reading the OP, I couldn't tell if R1 returned to 2nd as an effect of the OBS or whether R1 had reached/passed 2nd at the point of the trip/OBS.

NOTE: If R2 beat the throw to 1st, my guess would be that R1 would have beaten the throw to 3rd or only would have been beaten by the throw because of the OBS. But, was the throw to 1st from center?

If R1 stayed at 2nd because of the OBS and you judged R1 would have reached 3rd otherwise, R1 should get 3rd. In that case, it seems that R2 only returned to 1st because R2 was on 2nd and would have reached 2nd otherwise; then R2 should get 2nd.

If R1 stayed at 2nd and you judged R1 would not have reached 3rd even w/o OBS, then R1 should not get 3rd.

I don't see a pattern that would have resulted in R1 getting 3rd and R2 staying at 1st. IOW, if R1 would have reached 3rd; then it looks like R2 would have reached 2nd.

ditto to Andy's comments about mechanics