When the filler places a block, it travels through the air from the filler to the block space it will be placed in. During this window, breaking the filler deletes any blocks that are flying through the air.

BuildCraft version: 7.99.22
Forge version: 14.23.5.2815
Link to crash report or log: https://gist.github.com/TheDeviantCrafter/59a7329f77900ea77d4457908fe90f76
Singleplayer or multiplayer: Singleplayer
Steps to reproduce:

1. Set up a filler

2. Give it a small amount of power. The bug can happen with any amount of power, but this makes it easier to replicate since the items move so slowly.

3. Give the filler some blocks to place

4. Break the filler while the blocks are flying through the air.

On breaking the filler, we could have it replace any flying blocks with falling sand, so everything literally stops and drops