Some icons not showing?

For some reason, some icons do not show when I try to use them, such as ‘car’ and ‘sliders’, among others.

I’ve tried to replicate it but they show up correctly in your Code Snippet.

Is there any known issue that might cause this?

I never had this problem but off the top my head I’d expect it to either be a caching or file system/permission issue. Is that possible?

Yep it may be caching.
Web font with icons was updated as part of Webix 2.1 version, if you have older files or font file from older version is cached by browser then the above issue can occurs

Tried on both Chrome and Firefox, having cleared the cache on both. Still nothing.

Most icons work, it’s just a select few that don’t.

If problem still occurs - can you share a demo link where issue can be checked ?

If you have a support subscription - you can contact our support team directly at support@webix.com

I’ve sent you a message with the demo.

Issue was caused by wrong css file

Fixed, thank you.