The defect no longer shows up after I disabled Firefox extension AdBlocker Ultimate on Aliexpress.com site. It probably interferes with JS processing, despite being approved as compatible with Firefox 57. Similar effect was noted on some other sites when using this extension, after I discovered it blocks some Aliexpress content.
Adblockers being a user choice. We usually do not do outreach to the companies. Thanks for the followup arnymars. This is useful.