You need to look for "css_custom" attribute for featured box module. Other modules and CSS seem to work fine.
However, if you still don't make it work, then unfortunately we can't do much about it and have to wait from author to have some response.
As I mentioned earlier this plugin isn't on our compatibility list and has been closed a long time ago due to security issues, we can't do much about it without a cooperation from the plugin author.
The issue isn't with WPML. I'll advise to wait from an update from our compatibility team.
I've recorded 2 videos showing what to do and what's the problem. Please download hidden link, extract to get the video files:
1-homepage problem:
You can see that even after removing the css_custom from feature_box, there's still the problem with the page. So here are 2 options which you can try:
B) create a new page, add all content anew, remove the custom css and translate. Once it works, then remove the homepage (including translations) and set the new page as homepage. DO NOT duplicate the existing page, as I tried and it didn't work (this is however a separate issue).
2-test page:
As you can see the feature box worked out of the box. Why? Because custom css is very less, as I mentioned in the first video (as opposed to the feature box on your home page).
So the key point is, there's no way to identify which custom css works and which not - however, as a rule of thumb, remove the custom css which looks way too much (as seen in video #1).
Both videos show how to and what to look for. Other than that we've no trick available for now.
I request to wait for an update from our compatibility team.
Please friend I need your support!! I do something and seems OK but I need your help... YOU that followed my task and that you know your site
I've 2 issues with layout... items showed in box in home pages have strange spaces
Check in Home page EN hidden link
in "Our treatments" area blocks have white spaces.. even if I've all same blocks that I've in Italian version hidden link
So I've 10 block like in IT but with empty spaces... can you fix?
Check attached image
Same issue in this page hidden link
I've empty areas not filled (check second image attached)
As I requested earlier, the issue is different than originally reported (translation problem).
I recommend opening a separate ticket because as per forum policy we can only handle one issue per ticket. So you can get more to the point help, without mixing up several issues in one long ticket.
P.S.: I'll be off for rest of the week from tomorrow, but I'll keep an eye on the original issue and 'll update you accordingly. For any other issue, please follow as mentioned above.