Сollapse under the Mine Support

For the second time during the mining there was a collapse under the mine support.
The first time I did not attach any importance to this, just was surprised and made several screenshots:
Since this phenomenon does not happen again for a long time that I did not report this bug. But today it happened again. Again collapse in a safe radius of mine support. In general, I mining (was mining) a lot and I do not see much concern, on the contrary it is to add a little spice to the monotonous process. Just a reports about this bug.
Today's screenshots:
The first time I did not attach any importance to this, just was surprised and made several screenshots:
Since this phenomenon does not happen again for a long time that I did not report this bug. But today it happened again. Again collapse in a safe radius of mine support. In general, I mining (was mining) a lot and I do not see much concern, on the contrary it is to add a little spice to the monotonous process. Just a reports about this bug.
Today's screenshots: