When a boat or a minecart collides with a lava cauldron it'll get damaged by a wrong value (less than expected).

Steps to replicate:
run the following commands while staying in place:
/tick freeze
/setblock ~ ~ ~ minecraft:lava_cauldron
/summon boat ~ ~ ~
get outside the cauldron and observe the boat,
run /tick step 1

Expected behavior:
boat dies immidiately upon ticking (as it did in 1.21 and prior)
Observed behavior:
the boat doesnt die on the first tick and only dies on its second tick

This behavior happens for boats because since 24w33a boats miss their second collision check in their tick (before 24w33a they performed interactive collisions twice), to be precise it's in
Boat.java
in the
{{tick() }}
method.
here as shown in the pictures:
1.21 (there is a collision check):

24w33a+ (there is no secondary collisons check):

the same issue affects minecarts, they too are missing their second collision check in their own tick() method. (you can check how it was before 24w33a).

Please note that this is a tmc (technical minecraft community) sensitive issue. A lot of redstone contraptions rely on the ability of cauldrons to kill boats/carts upon their first tick of collision with the cauldron.

One way to fix this issue is to double the damage a cauldron can deal to a boat/minecart.
Another way to fix this is to put the secondary collison checks back into corresponding places.