When holding a fishing rod in your offhand, actions done in the main hand that cause an animation to play (mining or placing blocks, for example) will also have the animation play for the fishing rod’s line, despite being in the offhand.
Linked issues
duplicates 1
Comments 1

Thank you for your report!
We're actually already tracking this issue in MC-116379, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote or any additional information to the main ticket it would be appreciated.
Please be sure to use the search feature before creating a ticket to see if the issue has already been reported.
Quick Links:
📗 Tracker Guidelines | 🛠 Community Support | 📧 Mojang Support | 🔑 Account Support | ✍️ Feedback Discord