The bug
When you place a turtle egg onto a turtle egg while sneaking or a sea pickle onto a sea pickle while sneaking, you will add a sea pickle/turtle egg onto the block, however if you do that with candles, you will place it next to it instead of adding a candle to the block. This is inconsistent.
How to reproduce:
Place a turtle egg, a sea pickle and a candle
Start sneaking
Place a turtle egg by aiming onto the turtle egg
❌ You add one turtle egg to the block
Place a sea pickle by aiming onto the sea pickle
❌ You add one sea pickle to the block
Place a candle while aiming at the candle
✔ You will place a candle next to it.
Can confirm.