1k6/p1p5/8/1p6/R7/8/8/K7 w - b6 was created by Lomonosov but afterwards declared as Invalid position. 1k6/p1p5/8/1p6/R7/8/8/K7 w - - works just fine.
1k6/p1p5/8/1p6/R7/8/8/K7 w - b6 was created by Lomonosov but afterwards declared as Invalid position. 1k6/p1p5/8/1p6/R7/8/8/K7 w - - works just fine.