Regolith (mined) falls through

Currently, i use a setup of: Robo miner, above 1 row (2 tiles long) of insulated tiles, above that bunker door, and above the bunker door 2 rows of bunker tiles. 

And all of the sudden, once every few cycles i get the message, the miner is overheating. Why? because the regolith from above the 2 rows of bunker tiles, bunker door and insulated tiles falls onto the miner, causing massive heat. 

It never happens when looking at the construct, Always when i´m far away.