full steam ahead
playing quick draft thunder junction, opponent played Full Steam Ahead which says each creature can't be blocked by more than one creature, but would only allow me to block with 2 of my 3 creatures even though they were attacking with three creatures. No other effects influenced this. Unfortunately, this was my 3rd loss and I would have won on the following turn.

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rsi1859#31084 commented
I unfortunately didn't think to take a screenshot, but I went through every card that had ben played, and I was able to block all the opponent's creature, but only 2 at a time i.e. I could block creatures A&B, A&C, or B&C, but not all three, and there were no effects on any of my creatures, and all three could block, but again only 2 at a time.
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DAC169#34537 commented
Are you absolutely sure there were no other effects influencing blocking? In OTJ there's 3 different creature cards that can gain unblockable for the turn, 1 sorcery that can make a creature unblockable for the turn, 1 creature that can force opponents to have to pay mana for each blocking creature, 1 land that can make a creature unable to block for the turn, and 1 creature that can't block. THIS IS WHY SCREENSHOTS ARE SO HELPFUL.