Jarling Helm Bug?

I purchased the stunned jar and was augmenting it as i leveled up, but at lvl 143 it stopped allowing me to augment it. Is this a bug? Can I get rid of it and repurchase? i like having it in my build and Im not opposed to buying one of the other ones just dont want it to happen again on the next one and kinda want to exhaust all options on the current one first