Cart "change" button taking customers to Backlight login

Bit puzzling this (and a little concerning). If a user adds a product to their cart, views the cart and then clicks on the “Change” button, they’re taken to the Backlight login screen. I noticed this a couple of weeks ago, updated some modules and it worked ok, but just published an album from Lightroom and it’s happening again. Publishing is from LR version 9.2.1, PHP version 7.4.

Update, I re-saved the template and it seems to have corrected itself.