A project is created that has multiple issue types. For one issue type, the Component and Affects Version fields are not required. For another issue type, these two items are required. If you create an issue of the first type that contains no value for component or Affects Version, and then use the bulk operation to move it to the second issue type (staying within the same project), the following behavior is seen:

On the "update fields" screen (step 3 of 4 for the bulk operation), the component and Affects version fields will have a red asterisk, indicating they are required. The "Retain" checkbox will be checked, but will be grayed out so that you can't deselect it. When the user presses the "Next" button, errors will be shown on the Component and Affects Version fields indicating that these fields are required. There's no way to enter a value for these fields, however.

Workaround: bulk-edit the issues to add values for component and Affects Version, then do the bulk-move to change the issue type.