At random periods of time, when the player would interact with, place, destroy, etc. blocks, the visual update of the blocks has a delay of about a second.

When you'd place a block and point at it the outline would be there, but the actual texture not being updated yet (so basically has the texture of air ('nothing'). About a second later the texture finally updates. Uppon destroying the block the same happens. Texture of the block remains for about a second, but the outline is gone and you can walk through it (since it's air) and a bit later the texture actually becomes the one of air,

This appears to happen at random periods of time, so now it happens for some blocks, I do nothing for a few seconds, and then everything works fine again.