AP mesh and MX have nothing to do with each other. Nor does AP mesh cause layer 2 loops. And MXs don't run STP and therefore wouldn't have any loop detection mechanism.
What are the actual symptoms being seen when you say loops?
As for the page not saving perhaps there are some issues with configs on that page? For example do you have empty/unused Location and scanning Post URLs? Or, sometimes pages can have fields auto populated by some browsers with bad values and then the page won't pass validation & save. I've seen that before on the Network-wide page where things like an email address will auto populate in some random field.
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