Recently I looked up how to throw grenades underhand like you can in source, and started a local play to test it.
At the same time I also tried cooking them, but came across a pretty nade-breaking bug: they disappear if you cook them and they are set to explode before thrown/hitting the ground.

I've tried a number of things as a test:

  • Thrown without cooking: ~6s until detonation
  • Thrown with 3s cooking: ~3s until detonation
  • Thrown with 5s cooking: grenade disappears mid-flight just after being thrown
  • Just cooking no throwing: grenade disappears and character re-equips normal weapon.

After that, I restarted a local play to see if it was just that instance, but in the 2nd match it followed the exact same pattern.

Test point: Crossing spawn area (Security). Haven't tried other maps yet, but it smells like a problem with grenades themselves.