Portfolio carousel issue in Firefox

Hi,

I have a strange loading problem with Firefox (both on PC and Mac). When I visit pages with WP Bakery’s portfolio carousel, the carousel images (slightly larger) load beneath each other, instead of in carousel style. But if you just reload the page, everything’s look as it should. A bonus issue is that this is an intermittent problem; it doesn’t appear everytime (but almost).

I have tried inactivating all plugins, and change php version (I’m running 7.4), with no effect. Everything is updated to the latest versions.

My staging site: https://jsab.gangster.graphics/
All sites in the dropdown menus in the lightblue and yellow section are containing portfolio carousels, and suffer from this issue.

All other browsers I tested don’t have this problem.

Thanks!

(Maybe this is for WP Bakery to investigate, but their support forum is currently down.)