File existing activities to case

I created a custom field for an activity (meeting type). Then, I logged a new meeting activity for a contact (Tara Penner).

I opened a new case involving my contact and then saved it. Going back to the contact, I selected the meeting activity and tried to 'file on case'. The activity disappeared from the view, and was now showing up as part of the case, but the information entered into the custom field 'meeting type' was not carried over. Otherwise it was fine.

I was able to re-create this problem in the sandbox.

I'm not a developer, but I'll try to investigate and post any relevant information.

Thanks!