[Bug Report] updating expansion panels data causes incorrect index to be given

[gotenxds]

Environment

Vuetify Version: 2.2.23
Vue Version: 2.6.11
Browsers: Chrome 80.0.3987.163
OS: Windows 10

Steps to reproduce

in codepen:
Click the expansion panels, see index changes to 0 for the first panel and 1 for the second panel.
This is Ok

Click on the ADD MORE button, to add another item to the top of the list.

click on the first expansion panel, see that selected index is 2, but index of the item in the list is actually 0

Expected Behavior

Clicking on expansion panel should update with the correct index of the item in the actual data array

Actual Behavior

The expansion list is rendered correctly (in correct order) but items have incorrect indexes when updating v-model

Reproduction Link

https://codepen.io/gotenxds/pen/GRpWEvO?editable=true&editors=101%3Dhttps%3A%2F%2Fvuetifyjs.com%2Fen%2Fcomponents%2Fexpansion-panels%2F

[Mert75]

Kind of similar to #11405 where it happens on a VListItemGroup

[adatdeltax]

Has anyone found a workaround for this issue?.

[johnleider]

Duplicate of #8001

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