Mining a chest allows players to pick it up with all the items inside and carry it in their inventory. Also supports vehicles, tanks, and accumulators.
Not sure if the same mod mentioned above, but this also happens with the Merging Chests mod (https://mods.factorio.com/mod/WideChests). When breaking only the first chests worth of items are packed, the rest are deleted. When placed only a single normal chest is placed and not the remaining chests which were broken. If not fixable may be worth blacklisting Merging Chests entities to prevent this.
A recent API change lets me easily spill any items that don't fit in the chest, so now items shouldn't get deleted under most circumstances, but the Merging Chests interaction was broken for other reasons so for now I've also blacklisted it.
