Send copy of case activity is using the contribution receipt template - actually all message templates seem to be mixed up
Not sure what's going on exactly yet but can reproduce on dmaster.demo.civicrm.org.
- Create a case.
- Edit or create a case activity.
- In the send copy section pick a role.
- On demo it won't send an email but you can see the activity copy it saves on the case. In the details field it has the contribution receipt template message.
The template itself seems correct under admin - civimail - message templates, so the send copy must be loading the wrong one or something.
It doesn't seem to be a problem on an existing site that was upgraded, but I see it on PR test sites too as well as dmaster.