v18 Known Bugs
PayPal Payments Standard Mode
The mode PayPal Standard is not being saved (as seen below).
While it looks like the changes are not being saved, they actually are. Just make sure to check the option before you save. You can confirm the settings were changed by reviewing the PayPal Payments Pro mode, since both share the same setting.
Technical reason: Vue.js is confused and only setting a single radio on the page, instead of both since they share the same ids/names.