There is a maximum call stack size exceeded error https://github.com/liferay/yui3/blob/master/src/oop/js/oop.js#L349. I believe it's senna related and I've only been able to reproduce with Chrome and Edge. The issue is that 7.1 patched to FP-2 has this issue.
Steps To Reproduce:
1. Content > Web Content
2. Create Basic Web Content
3. Expand Schedule section
4. Click on time, click off, click on again to select another time.
Dropdown disappears after selection. There are no JS errors.
JS error is thrown to browser console, dropdown remains on the screen
Please note that the same is happening at picking time for date ranges
Firefox and Internet Explorer 11 not reproduced.
Master: Reproduced on Chrome and Edge 805b3bbe92c9a778475f6f40818cd52bb5037820
71x: Reproduced cba7661205e88225bd87ba9b506ab551d573ccd3
70x: Reproduced 32dc58f55c6310f45faac5784e185158397c5333