Hello,
My site is having two issues with dropdowns that may be related:
FIrst, unselected dropdowns will not show a default option and are instead blank. This is happening on all dropdowns on my site, including on a custom built /shop via the product categories widget as well as the category page (i.e. /product-category/test-category/). Here’s what that looks like:

Second, on the Woocommerce checkout page dropdowns are showing no default selected item as above and are also not showing field labels. Only the dropdowns are not showing labels. When the page loads I can see the labels briefly appear over the dropdowns and then disappear (as though display:none is being applied to them).

Possibly related to this is a mess happening at the bottom of /checkout at the payment options screen, where it looks like some code around PayPal and the button are being removed:

Current QA Status: This problem is persistent in Chrome, IE 11, and FF. Deactivating all plugins had no effect. Changing the theme to Twenty Seventeen removed all dropdown and cart problems. I can think of no changes I might done through the customization process that would have created this issue.
Any help you can provide would be very appreciated. I will private reply with site and access info.
Thank you.