Confounding Conundrum and Field of Ruin
Confounding conundrum recognizes the first land entering the battlefield as a result of field of ruin as if it was the second land, forcing you to return 1 land to your hand.

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SleepSort#35528 commented
This happened to me as well. Here's a screen shot including the game log and game id.
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CurvaceousKitty#99406 commented
Was playtesting Confounding Conundrum and I had this happen against an opponent. Would like to play with this deck but it is hard to test with a bug like this.
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Ajani1989#67697 commented
I had this issue and lost a league game because of it. I could not pay for my pact because it improperly had me bounce a land.
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bloscott#27455 commented
Yup, I've now seen this twice. Please fix soon, thanks!
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DrakeArron#10355 commented
I agree, this happened to me too. Especially annoyed as I was the conundrum player, so now I feel kinda bad xP