Recombinator issue: Exclusive Suffix can't be combined with T1 non-exclusive.

I've found a interesting bug which effects an item I have.

It's a Standard item which I've had from a few leagues ago.

The item in question has the modifier 'of the Underground', hence Delve. Minion Damage. Amulet base. No influence of any kind.

For some reason I can't combine this with any T1 Suffix at all:

Example:


On the other hand it can be combined with a T1 Prefix:


If anything else then a T1 Suffix is chosen the functionality is restored again, even with the same Affix as the example above:


Edit:
For some reasons the pictures from imgbb won't load, right-clicking the link to open the picture does work though.