Breaking the form

Hi Support,

We faced with an issue which was caused by LightSpeed Cache Plugin.

So here https://win4win.ch/fr/concours/jeu-concours-conforama/ we have a multi-step form.
The client reported the issue that it is not working.

We checked and figured out, that it was caused by adding a piece of code to JS (by LS), which is why the site completely breaks down.

– the first screenshot https://prnt.sc/ZCB7VvX_Bnsy shows two errors on lines 571 and 584. (This is the page where the error occurs)
– the second screenshot https://prnt.sc/GwZ15bJwpNr0 is the main version of the site (German https://win4win.ch/wettbewerb/drogi-ch-wettbewerb/) where this part of the code is not cached.

We fixed this on our side.
Please explain why this may appear to prevent possible cases in the future globally.

The page I need help with: [log in to see the link]