Not enough stone sword key bug

[rplsh78]

There's been a couple of times when I have 1 stone sword key in my inventory and it won't let me open the imp statue seal. Unless some of these require 2 keys, which none of them have stated such, I have no idea why it won't let me use the 1 key I do have.

[Greydalf The Gan]

Some of them do require 2 keys, like the one at the Roundtable

[Toffel]

if you look at the statue you can see if there is already 1 key inside. depending on visual you either need 1 or 2 keys. so yes your assumption was correct

[Fireserpent7]

If you look at the statues some of them will have a key already stuck in the heard of one of them and others will have none.