These have been around since the new shard bombs were introduced, and it's almost as bad as the stun bug was. Here's a video of it happening and it shows how easily reproducable it is:

http://www.youtube.com/watch?v=BL-1tH-cyp0

Here's a rundown on what I think is happening:

• The core of my first bomb is hitting. The game registers this as one hit.
• The core of my second bomb is hitting. The counter responsible for managing invincitinks has reset at this point and the hit is registered as one hit..
• The shards of my first bombs both hit. This happens very quickly after the core of the first bomb, and the game registers this as three hits. Seeing that the hit limit has been reached, the game now enables invincitinks.
• The core of my third bomb hits. This happens before invincitinks has died off.
• The shards from my second bomb hits shortly thereafter, refreshing the invincitinks mechanic.

This is a bug for three reasons:

1. The core is not supposed to be included in invincitinks. I quote Nick: "With the exception of the initial explosion, only 3 shards may hit a single target from the same bomb."
2. The third bomb is a completely different bomb, and should not be included under the previous bomb's invincitinks. I quote Nick again. It's even the same quote: "With the exception of the initial explosion, only 3 shards may hit a single target from the same bomb."
3. It's stupid.

There are a number of ways to fix this. Obviously I need to tell you this because you've had nearly a year to do so and you haven't been able to yet:

• Rework the invincitinks mechanics so they work exactly as described. Make a seperate counter for each bomb so that one bomb can't 'cause tinks for the other. I don't know the specifics of the Clyde engine. Maybe it's impossible, maybe it's not. I suppose it wasn't the easiest possible route seeing how you didn't take this in the first place.
• Disable cores from contributing to the invincitink counter.
• Up the invincitink counter to 4. While not completely removing the problem, it should make it much more rare.
• Unless you plan to seriously nerf certain weapons, just remove invincitinks entirely. Let me just pull up the maths for why there was absolutely no reason to have this fun-ruining, buggy mechanic implemented in the first place. All numbers taken from D24:
  • Combuster's charge does 547 damage + 5x166 damage = a total of 1377 damage. This is very easy to consistently perform every single charge attack. It can also set things on fire.
  • Prismatech Alchemer's charge does 383 damage + 4x3x198 = 2759 damage. This is a bit tricky to perform, but all you need is, say, two lumbers standing next to eachother or one enemy next to a wall.
  • Deadly Crystal Bomb would do 128 + 8x166 =1456. This would be literally impossible to perform on anything but Vanaduke, and even then you wouldn't be able to hit with the core. Making it further impossible is disappearing shards that would render the player unable to actually gather the shards and hit the same enemy that many times with it.

Incidentally, alchemers are ridiculous.

Edit:
Herped the math a bit.