I've spent 3 diamonds on upgrading a SilentGear katana, but it's not getting any new attributes. Meanwhile, the Parry This! mace took exactly one diamond to upgrade.

Is something bugged, or am I just having rotten luck?

...and then the moment after I opened the issue, I went to try one more time and got a crit modifier. It's not a bug, false alarm.

Rotten luck!

The default chances of rolling each attribute is something like 5% to not overpower items