Behaviour overwrite other behaviour script

Steps to reproduce the problem

1. Create a new Behaviour and add a custom field named "test"
2. Add code like this and save it:

   log.warn "Script 1"
   

3. Click Behaviour on the left menu
4. Create a second Behaviour and add a custom field named "test"
5. Open the field script and we see the logging from step 2.
6. Edit the code to this and save it:

   log.warn "Script 2"
   

7. Go back to the first Behaviour and the script being overwritten by the second behaviour script.

Demo -  Screen Recording 2020-06-18 at 1.18.36 PM.mp4

Jira 8.3.1