Ajax error: Cannot read property ‘both’ of null

Hi there – I have a strange situation where everything works great in my staging environment (supposedly identical), but in production I get the following error (only for logged-in users):

Uncaught TypeError: Cannot read property ‘both’ of null
at Object.success (no-dislike-comments.js:19)
at i (jquery.js:2)
at Object.fireWith [as resolveWith] (jquery.js:2)
at y (jquery.js:4)
at XMLHttpRequest.c (jquery.js:4)

Example URL w problem: https://www.velominati.com/vsp/velominati-super-prestige-womens-liege-bastogne-liege-2017/