One of the biggest advantages of using blocks for repeated content in drawings is their “togetherness” – where one piece goes, the whole thing goes. That unity can disappear in a flash, though, if the block is exploded.
Depending on the type of block, this can either be necessary (say, for a detail from your library that you need to edit) or a disaster (anything with attributes).
Since the introduction of dynamic blocks (which are especially bad to explode), you’ve been able to prevent blocks from exploding at all. Instead, you’ll get a message telling you the block “could not be exploded.”
How do you apply this (wonderful) setting? Two ways.
First, when you go to create a new block, there’s a box to un-check in the Block Definition dialog.
(I’m also a fan of checking the box above it, to force the block to scale uniformly, but that’s a topic for another day.)
Second, for an existing block, there’s a setting in the Properties palette inside the Block Editor. With no objects selected, look for the Block section, and change “Allow exploding” to “No.”
Once you have this set for all the blocks that should never be exploded, you’ll be able to breathe easier—no more risk of inadvertent block breakdowns!