When I tried to repair my damaged shield on anvil with crimson planks, the result is none, meaning that crimson planks cannot be repaired with crimson planks. And perhaps warped planks cannot repair shield on anvil either.
(I actually don't know whether this is a bug or "work as intend", so I report this situation)
Thank you for your report!
We're tracking this issue in MCPE-82395, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki