Copying price set creates incorrect price field dependency

When creating a copy of a complex price set containing 5 price fields, the copy has an unwanted interdependency between two of the price fields that is not present in the original. Choosing an option from field A hides all options from field B and vice versa. Fields C through E are unaffected. At this stage I have not linked the price set to an event - I am simply looking in the preview of the Price Set.

I have looked through all entries in the price_sets, price_set_fields, and price_set_field_values tables, and can see no difference between the two price sets, other than the key fields.

Deleting the clone and repeating the copy action results in the same behaviour. I am now looking at creating the clone from scratch instead, but would love it if there was an explanation or (if it's a bug) a fix available.

Incidentally, dependent fields in price sets would be a great feature - does it exist?