Contribution Page forms don't throw up error pop-up on form rule errors

Steps to reproduce the issue:
Go to Contributions=>New Contribution Page
Enter a Title and select Member Dues for Financial Type. Click Continue.
Go to the Memberships tab. Put a tick on Membership Section Enabled. Scroll down and put a tick on Require Membership. Leave everything else as is. Click Save.
Go to Manage Contribution Pages. Click on Configure=>Membership Settings for the page you just created.

Observed behavior:
Form has not saved the data.

Expected behavior:
Form should either save data or display a message that the entered data could not be saved because of such and such problems with it.

Additional info:
From testing on my local it appears that the data does not get saved at all in the relevant table for the Membership Settings data (civicrm_membership_block). Sometimes, when certain settings are selected in the form, it saves. With other settings selected, it doesn't save. From this behavior my suspicion is that CiviCRM sees a problem in the data I've submitted, however there is no error message that tells me that. So I, as a user, am at a complete loss as to why it's not saving the form when I save it.