Trading buttons for villagers, and board buttons for boats, do not show up in the new UI unless the entity is hit or is extremely near to the player (about 0.3 blocks or less.) This is extremely annoying in the case of villager trading, as hitting the village will cause it to increase trading prices, and sticking too close to the villager causes it to be pushed away. I hope Mojang will fix this soon.
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We're tracking this issue in MCPE-162846, so this ticket is being resolved and linked as a duplicate.
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