Unable to remove seals from Longsword of Light

I just noticed that Longsword of Light is unable to be chosen when picking the Remove Seals option at the research base(even though every other weapon I have is selectable). I got the seal shapes messed up on it and would like to fix it, but I guess the weapon is a dud if I can't fix it now.

I searched on Reddit and couldn't find any info, strange enough(you would think people would be talking about this), and tried googling it, but Google is nothing but an AI-ridden cesspool now, just keeps bringing up AoC topics...so here I am, hoping I'm being dumb and there is a fix to this.