Membership level not added to new group

[michaelbeil]

Describe the bug
A membership level is not added to a new group as reported in ticket 332225 (moderators only):

... when I create a second group (Added Access in our case), I can’t drag and drop anything from the main group to the second group correctly. As in the screenshot I first sent, one level will go in the right place (though the divider is dropped half way down) and then the second member level I drag down into it left-aligns and will not move over into place. Also, nothing stays in the second group when I leave the Levels tab. It is always empty when I open Levels again.

To Reproduce
Steps to reproduce the behavior:

1. Drag and drop a Member Level into a new group,
2. Refresh the levels page and that membership level is no longer available in the new group.

Screen video

Expected behavior
I expect the membership level to be in the new group.

Isolating the problem:

• I have deactivated other plugins and confirmed this bug occurs when only Paid Memberships Pro plugin is active.
• This bug happens with a default WordPress theme active, or Memberlite.
• I can reproduce this bug consistently using the steps above.

WordPress Environment

``` PMPro 2.5.7, WP 5.7, PHP 7.4.1, and MMPU 0.8 ```

[michaelbeil]

A different customer in ticket 334166 (moderators only) is experiencing this:

I set up two membership groups and the “main” group is the 1st membership group in multi-membership group settings.

After updated to WP v5.7, when I tried to assign membership to members manually in the admin, it shows no membership level in “main” group but looks okay in the other group.

When I tried to move membership level from “main” to the other group or add new membership level to any group, I receive the error message, saying the membership level was not yet in any group and has been added to the 1st group found, which in my case is the “main” group.

[michaelbeil]

This is also mentioned in #91.

[michaelbeil]

A different customer in ticket 460442 (moderators only) is experiencing this:

Using the Multiple Memberships per User add-on (yes, I know it is marked as in “beta”), I cannot move one of the Membership Levels to another group and have it “stick” — i.e I change the group and leave the Membership levels page, but when i return it is back to the same group. Oddly enough, the new group I want to move it to also has a Delete button next to the Edit button, while none of the other 3 groups I have do. I have Deleted and recreated the new group, but no change.