Native Dynamic Placeholders overlap on the Experience Editor

Question

I am using the Sitecore 9 default implementation of Dynamic Placeholders, and everything works fairly well. However, the one issue I've had is that the Dynamic Placeholders all overlap each other in the Experience Editor, making it very difficult to actually add content to these placeholders. Thus far I have been unable to find a cause for this.

My code is as follows:

---

On the main page:

@Html.Sitecore().DynamicPlaceholder("modules", 5)

---

On the module added to the first dynamic placeholder:

@Html.Sitecore().DynamicPlaceholder(new DynamicPlaceholderDefinition("cards")
 {
     Count = Model.CardCountPerRow,
     OutputModifier = (input, context) => new HtmlString("<div class=\"" + Model.ColumnClass + "\">" + input + "</div>")
 }

Has anyone else encountered this and is there a way to fix it?

Update: It appears that when I add different types of modules, they appear correctly. It is only when I try to add multiple instances of the same module type that they overlap each other.

Answer 1

So, after wrestling with this for awhile, I finally figured out what the problem was. It seems I had forgotten to assign a placeholder setting to the dynamic placeholder, which then caused rendering issues since the Experience Editor couldn't tell the difference between the dynamic placeholders. The reason it displayed correctly when the placeholders were empty or when the placeholders had different modules plugged in was because the EE could then see that the placeholders were indeed different and not the same.

tl;dr - Make sure you assign a placeholder setting to your dynamic placeholders!

Edit: I also found that the EE was interfering with my CSS and JS, so I was able to make some changes that corrected some of my rendering issues.