It's not possible to switch between 2 types of protection: agentless and agent-based. Agentless and agent-based types of protection are using incompatible methods of changeblock tracking.
It's also not recommended to "double-protect" the same VM with agentless and agent-based protection at the same time. When VM is protected agentlessly, agent software should be uninstalled from the guest OS.
When switching from one type of protection to another, please delete the machine from protection first, leaving recovery points intact, then protect the machine again using a different method of protection.