The bug

Modifying the maxCommandChainLength gamerule value inside a function or command block does not affect the currently running chain.

How to reproduce

1. Download the attached file MC-124447 datapack.zip and place it in the datapacks folder of your world
2. Set the maxCommandChainLength value to 2

   /gamerule maxCommandChainLength 2
   

3. Use the following command

   /function custom:modify_max_chain_length
   

   → It executes only one command

4. Run the function again
   → Now it executes both commands