Multiple Checkbox do not update if all values exist at the start

[SimeonC]

Describe the bug
When using the non array version of multiple checkboxes, (<input type="checkbox" {...register('sharedName')} />), if values are set using defaultValues then they cannot be reliably unset. This only seems to occur in the v7.6 version.

To Reproduce
Use this sandbox for the following scenarios; https://codesandbox.io/s/youthful-haze-rx39o

All selected as default scenario:

1. Using meal1, try to deselect any of the checkboxes
2. The watcher doesn't remove the values from the array
3. Submitting the form doesn't remove values from the array

Some selected as default scenario:

1. Using meal2, try to toggle the checkboxes
2. In the watcher, lunch and supper are always present ignoring any other values
3. Breakfast and dinner can be toggled correctly.
4. Submitting the form gives the same results as the watcher

No values selected as default:
meal3 ([]) and meal4 (undefined) work correctly and are there for counter examples.

Codesandbox link (Required)
https://codesandbox.io/s/youthful-haze-rx39o

Expected behavior
All default value combinations should work consistently allowing default selected checkboxes to be deselected.

Desktop (please complete the following information):
(I think this is unrelated to at least browser)

• OS: OSX
• Browser safari, chrome
• Version 7.6

[SimeonC]

This only occurs in version 7.6, version <= 7.5 works fine.