From ENTMQBR-8618 we have an out of sync problem when there are duplicate entries in the CR brokerProperties field as the check sum does not suppress duplicates but the broker does not see the duplicates are the java properties reader drops them in favour of last one wins. We do some sanity checks on the contents of the properties already, we could add a check for duplicates.
On the contents of external or -bp extra mounts, I guess we could do the same sort of checks.