Straight follow, via Jamba works.
Not sure on your addon.

If you disable addons entirely.
Target one toon with another, and click /follow, it should work.

With a focus based system.
Have a hotkey for each toon.
So when you PiP (Keyclone Maximizer) switch from A to B.
It makes B the focus on both A and B (as well as any other accounts, if there are more then two).
Likewise, when A becomes the active/lead toon, A is the focus on every account.
Then your follow should be something like:
/follow [target=focus]

That should work.

You could check if the addon has a more up to date version.
You can also check (in addons) to run out of date addons.
Which won't always work, but does quite a bit.