Override JS options in the Foundation tab won't be cached properly for modular pages, referenced here:
getgrav/grav#507
The "Foundation" tab needs to be removed from all modular template blueprints using the "ignore" field:
http://learn.getgrav.org/advanced/blueprints#special-form-fields-available-only-in-admin
The "ignore" field will remove all options from the tab, but not the tab itself:
getgrav/grav#620
This is a functional solution for now and needs to be included in the next release, but it would be nice to remove the tab totally.