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The cause is the perfmatters plugin and its reckless use of the outdated “FastClick” script, which improperly overrides click/touch events on mobile. FastClick hasn’t been useful for over a decade and only adds bugs and bloat to a site. From the authors of FastClick:
Note: As of late 2015 most mobile browsers – notably Chrome and Safari – no longer have a 300ms touch delay, so fastclick offers no benefit on newer browsers, and risks introducing bugs into your application.
No plugin or theme should be using FastClick. Report it as a bug to the author(s).