selectButton >Custom Template broken

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Plunkr Case (Bug Reports)
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Current behavior

Using Custom Template with selectButton does not work properly anymore in v11.2.1
Selection does always select ALL available options. Does not deselect any options.

Expected behavior

Selection and Deselection of items properly. (e.g. V 11-rc1)

Minimal reproduction of the problem with instructions

In your showcase
https://www.primefaces.org/primeng/showcase/#/selectbutton
you can see falsy behaviour

What is the motivation / use case for changing the behavior?

Please tell us about your environment:

• Angular version: 5.X

• PrimeNG version: 11.2.1

• Browser: [Chrome 88]

• Language: [all | TypeScript X.X | ES6/7 | ES5]

• Node (for AoT issues): node --version =