Hi. Not bug in Helix, but your HTML/CSS skills.

Instead of...

.speasyimagegallery-album img { border-radius: 10px; }

.speasyimagegallery-gallery-item img { border-radius: 10px; }

... try to use

.speasyimagegallery-album > div,
.speasyimagegallery-gallery-item > div {
    border-radius: 10px;
    overflow: hidden;
}

Tip: Do not use the "Custom CSS" field in Helix Framework, because it adds the whole code to head. Which leads to cluttering and worsening performance. Use custom.css file instead of it.

"Custom CSS" field in Helix Framework should be used in rare cases for a small volume of code, to which you want give the highest priority, when you use several copies of the template style.

For example, if you want that in the first template style the menu will be red and in the second template style the menu will be green. Then you can use this field.

Yes, staff employees often offer to add code to this field. But in my opinion, such a proposal speaks of unprofessionalism of an employee or laziness for a more detailed explanation.