The error:

When using /execute positioned, which as you know, offsets the position of an entity, it no longer executes recursively, and no longer offsets properly.

To reproduce:

1. Download the data pack below.
2. Type in /function recursion:ray.
3. See that no block is placed where you look.

Let's go through this error.

What this function attempts to do:

Is a block of air in front of you? (Local coordinates)

If there is air, then it offsets (Local coordinates), and runs the function again.

If there is not air, it sets a block at said position.

This should produce the results of placing an emerald block at the closest solid block you are looking at, as each time, it offsets, running the function again, searching in front of you again for said solid block. However, this offset is not applied in the recursion of the function, and it just does nothing, unless there is a solid block directly in front of you.