When mining Nether Quartz we noticed that we couldn't always see the same Nether Quartz. There were blocks we could both see, some only I could see and some that only player 2 could see. when one of us tried to mine the nether quartz that look like nether rack it would turn to nether quartz at the last second break into nether rack reappear and we would have to re-mine it. The glitch tended to happen in veins of nether quartz not just to single pieces