[Appointments+] Working Hours & Exceptional Working Days don't save/update

When attempting to save a user's Working Hours, Break Hours, Exceptional Working Days, & Holidays (on the user's profile), the settings don't seem to save. Particularly what I've noticed is: if you try to change only one of the individual sections the changes will save. However when saving multiple sections at once only some will save. Let me explain. For example if I make changes to Working Hours and hit save the changes will save. However if I make changes to Working Hours AND Break Hours, only Break Hours changes will be saved. The same applies to Exceptional Working Days & Holidays. If I try to save both sections, only Holidays will be updated.

I can replicate this every time. Using the latest version of Appointments+ (2.3.1) with WordPress 4.9.6 on PHP 7, with max_input_vars set to 8000. I have already done conflict debugging and disabled all plugins and used the 2017 theme. Problem still persisted.