Slider only shows up after hovering/scrolling on the page

WP Rocket

This problem is commonly caused by WP Rocket. It has a Delay JavaScript execution option, which makes your JavaScript codes to run at a later time, based on some rules they think should happen, but these aren't happening in some cases and the code either never runs or with a very big delay or after some user action on the page, like scrolling or hovering. 

Solution

You should try to exclude us from WP Rocket, maybe just from the delayed loading to see if that solves the problem. But if it won't, try to turn off this feature from them, or maybe just for a test, try to turn off WP Rocket completely.

Nitropack

The issue has came up at Nitropack too. You should exclude us from their optimization.