Issue title: bug: ion-select
 Issue body: I use ion-select of Ionic on my application and I find an error on this.
This error is random and she's present on <ion-select interface="popover"></ion-select>.
When I select a value on my ion-select and I click on an other field, sometimes my value selected to modify alone.
I've test on Ionic's documentation and I reproduct this error...
If I choose a value in gaming field and I click on an other field, Month for example, the gaming field change without selection of my part.
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{'source': 'GithubIssues', 'repo_name_with_owner': 'ionic-team/ionic', 'issue_id': 493939625, 'repo_stars': 14016.0}