total upkeep premium plugin causes Site Health critical' error

Thank you for reporting this to us Andy!  Just to confirm, you're referring to this message in the Site Health area when Total Upkeep is activated, correct?

If so then our team is currently aware of the issue and we have a ticket in to address this. Fortunately this bug does not appear to have any actual effect on your website's ability to handle automatic updates and you should be able to manage updates as expected.

However, please let us know if you notice some degradation in functionality that we might have missed in our own testing and we will see if we can diagnose the problem.