When attaching a chorus plant to a chorus plant at the top and any of the four sides, the centre plant and the other one break.
Steps to reproduce:
1. Place a chorus plant on end stone or another chorus plant
2. Attach another plant either on top or next to it
3. Place the final plant in the other position
What I expected to happen was...
That all three would remain
What actually happened was...
The first and second plants broke, the last one placed remained