On Ask Ubuntu, there was a question that was flagged as spam, and handled by a moderator as Declined as it was not spam. Later the same day, another flag (VLQ) was raised by the community, and another flag later raised of the same Spam type.
It was not possible to invalidate only this new Spam flag while leaving the VLQ flag alone, which was my intention. Normally, we can select the individual flag and handle it individually. However, because an earlier flag came in, it was lumped in with the same, already invalidated, flag type and could not be individually selected for handling.
The way I fixed this was to handle the VLQ flag manually, and then go into the flags queue and mass-handle all flags on that specific post itself rather than handle them individually. This is fairly annoying if we want to handle some flags of one type and leave others alone. It's a minor annoyance, yes, but it should probably not be working that way? (Perhaps, instead of lumping them together, if one's already been invalidated open a new line for new flags of that same type?)