An impulse command block is given the command fill ~ ~1 ~ ~ ~1 ~ air 0 destroy and a chain command block after it is set to conditional and is given the command say active, and a block other than air exists above the first command block. If the first impulse command block is activated then the second conditional chain command block will not activate. This appears to be the cause of the destroy oldBlockHandling because without it the second command block activates without issue.
Example Gif