Adding achievements manually doesn't work

[GNS7]

I only get this error when trying to add achievements for a new game

and this too, it's in portuguese, but basically means, object reference is not defined for object instance

Is there anything I'm doing wrong?

[avalconi]

I get the same error message, "Object reference" one, when trying to add achievement for a new game on version 3.1.7.
I downgraded the plugin down to 3.1.5 version and it seems to work.