I need help with media queries set directly inside of column options. I set column sm-12, md-6 and lg-3. Small and Large seems to work, but Medium doesn´t. How could I solve this with using the right-side-menu and not writing own media-queries ? Could it be that it´s a bug ?
Are you using the Options panel to set your column sizing and visibility or are you adding classes to your columns manually? If manually, remove those and go to the options panel and set your settings there instead so that the settings pick up "all" of the settings that go with it.
If you're doing it that way already, give us a step by step to tell us what you're doing, or upload your site and give us a link so we can look at it and get a better idea of what it might be.