When using the "Override user style choice" on a node, any time you view that node or node content the light/dark/system switcher is disabled.
It'll inherit whatever was selected from the previous style, though, interestingly enough.
Confirmed the style set on the node has variations enabled...
Have you already created a ticket with us already? If not, feel free to reach out here: https://www.audent.io/contact
Another person on the team I believe is familiar with the issue and should be able to help.