Thanks @SuatB, this brings me in the right direction. I had already excluded the Slider “Splide” CSS and JS files from WP Rocket. I have now added the Bricks scripts to see, if this improves the page load and fixes the flickering.
For reference:
Bricks Slider:
/wp-content/themes/bricks/assets/css/libs/splide.min.css
/wp-content/themes/bricks/assets/js/libs/splide.min.js
Bricks Builder:
/wp-content/themes/bricks/assets/css/frontend-light.min.css
/wp-content/themes/bricks/assets/js/bricks.min.js