Odd behaviour with markdown card

[Hitman247m]

Hi,

I've been using your themes for a while, and everything is great. Sometimes, when refreshing the page, I end up with odd shading around the markdown cards. Here's what is looks like when it "breaks":

Here is when it loads correctly:

This happens pretty randomly, and I can usually make it happen after refreshing a few times.

Here's the config for the card:

type: custom:vertical-stack-in-card
cards:
  - type: markdown
    content: <h1>Switches</h1>
  - type: markdown
    content: <h2>Lights</h2>
  - type: markdown
    content: <h3>Main Floor</h3>

Not sure what's going on, and would appreciate some help if you've seen this before.