Firefox has very big delay on tap until click event gets triggered

I'm seeing a big delay of seconds after I touched a <a> element in Firefox (54) until the click event gets fired. On Mouse Click I don't see any delay.

I'm using jQuery's $a.click( event handler, but I have the same behaviour if I use the native a.addEventListener.

I tried to analyse it and recorded when touchend event is fired and how long it takes until the click event gets fired.

I'm getting quite mixed results – from 10 to 7000 ms between the touchend and click. An alert is showing the delay, and after that the rest of the click handler is still executed quite late.

Also when using browsersync, and tapping the element on my phone, I see a reaction in the other browser immediately – but the phone firefox doesn't react for seconds.

Thanks for any hints on why the execution could be delayed so much.