The design for this one is meant to be buy all to get Diego it is a cheap ploy instead of putting him as the completed bag or whatever. Look here.
His odds at 0% are not a bug it’s intended you get him last.
Thank you for contacting us.
I understand that you are may be confused as to why Diego’s odds is displaying as 0% in the Diego Stash.
Please be advised that the first open odds for anything in a stash is greater than zero and all items within it have a chance to drop.
For each open of the stash, the odds for every item will increase as other items are removed and opening the full stash guarantees every item within it. This means that Diego is guaranteed if you open the full stash.
I hope this information helps!
Should you have any other concerns, please let us know.