The Bug:

The resin brick stairs is made with 6 blocks in a crafting table just like other stairs, but instead of the expected 4 stairs we can only get 1 single resin brick stair, which is inconsistent with other stair types.

Steps to Reproduce:

You can also use the test world to reproduce, it may be helpful to watch the video first. 

Main way:

1. Open the latest Minecraft Preview build.
2. Press the "Play Preview" Button.
3. Create a new world. It is best to start in creative so you can easily reproduce this bug.
4. Open the creative inventory.
5. Go to the "Construction" tab of the creative inventory.
6. Get some Resin Brick Blocks. You need at least 6 resin brick blocks.
7. Go to the "Items" tab of the creative inventory.
8. Get a crafting table.
9. Exit the creative inventory.
10. Place the crafting table you just obtained.
11. Open the crafting table you just placed and try to craft Resin Brick Stairs.
12. Look at the input and output of the recipe.

Alternate way - Using test world:

1. Download the attached world.
2. Follow the signs. The signs tell you what to do.
3. Look at the input and output of the resin brick stairs recipe.

Expected Result:

The crafting recipe of resin brick stairs will produce 4 stairs as the output, which is consistent with other stair types.

Observed Result:

The crafting recipe of resin brick stairs will produce 1 stair as the output, which is inconsistent with other stair types.

Notes:

This bug report has more detailed information gives steps to reproduce in more detail and has expected/observed results in the report itself along with a test world and a video, unlike MCPE-187796.