Brutal Doom 2 - Master Levels - Pistol Start - Hard Realism - Bad Dream (BADDREAM.WAD, level 21)

In the Brutal Doom version of this map, there is a major lag "spike" when you grab the invulnerability and the ceiling starts coming down. I was able to wait out the lag spike, then allow myself to be crushed before the invulnerability wore off, then finish the level. Despite that, it kept showing items at 60%, but I combed the map and couldn't find the other two. It's possible they were drops by the cyberdemons, which disappeared after they were crushed.