I was able to replicate this bug in version 2.8.7.
So this may not be fixed completely.
To replicate I had an existing barbarian/ha-cluster installation.
Removed the relation between these charms which resulted in ha-cluster being removed.
I then recreated the relation and the VIP was grabbed for the subnet IP for the charm which had the pre-existing VIP running.
I was able to replicate this bug in version 2.8.7.
So this may not be fixed completely.
To replicate I had an existing barbarian/ ha-cluster installation.
Removed the relation between these charms which resulted in ha-cluster being removed.
I then recreated the relation and the VIP was grabbed for the subnet IP for the charm which had the pre-existing VIP running.