Block item lighting glitch

Is this also an issue with smooth lighting turned on?

Without smooth lighting, the engine is more buggy than with smooth lighting, which could potentially be your issue.

I have not tried with smooth lighting. I can't either because my game lags so bad.

Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.

Fast lighting is not meant to look especially nice. If you want great looks, fancy lighting is the way to go.

This ticket has been marked as a duplicate of MC-10135, in favor of the better description/information provided.