We don’t use a caching plugin and we purge all cache on our hosting before testing (and obviously remove all browser cache).
I’ve purged and tested again and it persists with the child theme off. Here’s the screen recording of the latest test: https://we.tl/t-gYxt7lhIEM
Apologies, our developer has turned it back on by mistake. It’s off now, please try again. Caching is off on the server and we’re not using caching plugins.