Important bug with "Restricted days" availability feature

Hi, I just reproduced this on a fresh install with updated plugins, this feature is definitely broken, and it works in admin dashboard without wcfm.
Way to reproduce:

1. go to wcfm dashboard -> products -> add new
2. choose appointable product type, add title, scroll down to availability tab
3. check “Restrict start days?”
4. add monday, tuesday, wednesday, thursday, friday to “Restricted days”
5. add Recurring Time(all week) type custom availability, 10am to 6pm for example
6. click submit, and view product page

You will see that Friday and Saturday became inactive, instead of saturday and sunday.
And it’s not just a labeling issue, ANY day you take out will be interpreted as Friday.

7. Go back to wcfm dashboard, edit the same product again.
8. The “Restrict start days?” checkbox is UNCHECKED again, even though you just checked it in step 3.
9. Go to wp admin dashboard, edit the same product, and save it.
10. Go to product page

This time it works perfectly, so it doesn’t seem to be a problem with the WC Appointments plugin.
(same feature works fine with wcfm + wc-bookings plugin, strangely enough)