Hi there!
Thanks for reaching out to us.
Is your helix, SPPB, and everything up to dated, please? Kindly check and do the updates if anything is left. After update and clearing caches, if there is still some issue you can use custom CSS.
However, for now the following custom CSS can help though:
body.ltr .sp-megamenu-parent>li.sp-has-child>a:after, body.ltr .sp-megamenu-parent>li.sp-has-child>span:after {
font-family: "Font Awesome 5 Free";
}
Here is all about custom code placement in Helix Ultimate: https://www.joomshaper.com/documentation/helix-framework/custom-code-css-js-meta
Best Regards