I kinda hope it's only me, but this is what happens:

I created a new field and subfield 991$a, linked to CCODE for testing.
The field and the subfield are marked as repeatable.

Problem 0: 
- Try to repeat the field without filling in a value
- It will not work, there is a JavaScript error message:
TypeError: divs[i].getAttribute(...) is null  cataloging.js:100:12

Problem 1:
- Select a value for the subfield.
- Repeat the field.
- The value is copied form the original field into the repeated field (should be empty).

Problem 2:
- Try to clear the value in the repeated field using the X in the pull down.
- It won't work.

Problem 3: 
- Try to open the pull down in the repeated field
- It won't work.