Eduardo Francisco Castillo Zapata

So, I made a copy of my world and put in on creative to make some testing.

First I unleashed all allays and didn't have any other mobs in leads, this didn't make any difference.
Secondly, I removed the noteblock I had set the allays to deliver the items to, it was powered by a sculk sensor and the allays themselves set it up so the noteblock was on loop, this didn't stop the slowness of minecarts. Then I killed all the allays I had and unsurprisingly this got rid of the slowness of the minecarts and everything was back to normal, but kind of anticlimatic because I love my allays, so after that I spawned tons of allays and this didn't cause any slowness in the minecarts, then I gave them all (the same type of) seeds and this didn't cause slowness either, it was after I started dropping seeds that I noticed the minecarts were moving slow and the seeds I was dropping were falling slowly, but after the allays gave the seeds back to me everything seemed to be back to normal, so this got me wondering 'why is it that after the allays are finished returning the seeds the minecarts were moving normally again this time but why weren't they moving normally when the original allays that were holding the flowers were alive even if they weren't trying to reach items because I made sure to kill all dropped items?' [this test was inconsistent with the next one because the next test I gave them all the same item except this time I gave them "Allay Spawn Egg" instead of seeds and the only thing that changed was that I moved maybe 20 blocks to where this test was made].

After that, I made another copy of my original world and I took away all the items the allays were holding and this turned everything back to normal, then I killed all dropped items just to make sure they're not trying to reach for anything, then I gave them their items back and the minecarts were moving slowly back again, so I took all the items back and only gave items to 4 allays and it was enough the make the slowness effect of the minecarts come back. Then I killed these allays (that were the originals in my survival world), replaced them with 9 new ones and gave them all the same item, this time it took more allays with items to make the slowness come back.

So, in summary this bug makes minecarts and I noticed all redstone componentes to react slowly, also dropping items makes them fall in slow motion too, it probably has not much to do with leads, it's definitely the allays that were holding (different) items, the ones that were holding the same item caused less trouble and I made sure that there were no items they were trying to reach so it's different from the MCPE-147882 issue but definitely similar, maybe they're constantly searching for items even if there are no dropped items?

this is happening to me too
🙂 I hope they fix it soon

Just making sure. You have to use the campfire one block below the bee nest, I don't know if it's meant to be that close for it to work but thats how it worked for me, I used to put the campfires more than two blocks below but they didn't work