Dubious best move by engine

I am puzzled why engine says Ne6+ is best move and not Rb1. Doesn't that lose a knight for nothing (although still winning for white) ?

You are puzzled why the engine says that, when you literally have the engine analysis open right in front of your eyes and you can just check it at any time?

It does not get any more bizarre than that.

@magipi  You really think I did not check the line suggested by engine ? The suggested 'best line' just says you lose the knight for no reason and then go on with the game. I am just reporting some kind of a technical engine glitch here unless of course there is something deep (which I really doubt) in which case I'd appreciate a helpful chess comment instead of a bizarre one  

If you check the line, you'll see what the engine's idea is. After Ne6+ fxe6, the engine will play Rb1 anyway, than Rbxb6(!), creating a battery on the 6th rank, then take at least 2 (maybe all 3) of the black pawns. It sacrifices the knight not "for nothing". It gets some pawns and exposes the black king.

Is it better than keeping the knight? No. Any decent engine at any decent depth will tell you that Rb1 is better. Even the weak chess.com engine will tell you that if you give it a few seconds. But Ne6+ is the second best move, and at low depth of analysis it is seen as best. There's no glitch here.

@magipi Thanks for the helpful comment! The low depth analysis makes sense here. To be precise I should rather say it's a glitch at depth 18 analysis, which is corrected at a higher depth for example 30.