SonSon PCB question

[kamex]

I've had this SonSon PCB for a couple years at this point. It seems to play fine (I 1cc'd it once), but I've noticed a strange bug. On semi-rare occasion, a letter will spawn in the play area. You can't interact with the letter and it just scrolls to the left like any other game object.

So... can anyone who has this PCB confirm whether or not this is abnormal behavior for this board? Thanks!