The bug

When using the start_riding, summon_ride, or summon_rider overloads of /ride, the operation correctly happens instantly. For example:

/ride @e[type=minecart,c=1] summon_rider pig
/kill @e[type=pig]

The second command successfully kills the pig, because the command works right away.

However, the stop_riding and evict_riders do not work this way. They take one tick to resolve. This is a huge issue when using functions, which have no elegant way to delay commands in Bedrock.

How to reproduce

Set up a command block chain with the following commands:

/ride @e[type=minecart,c=1] summon_rider cow
/ride @e[type=minecart,c=1] evict_riders
/ride @e[type=minecart,c=1] summon_rider pig

Now summon a minecart and activate the chain.

Expected behavior
A pig was spawned riding the minecart

Actual behavior
No pig was spawned. The command block feedback message reveals that the minecart was full. This is incorrect, since its riders were evicted in the previous command.