"Safe mode" popup: imperfection on popping-up

[ildar170975]

Checklist

• I have updated to the latest available Home Assistant version.
• I have cleared the cache of my browser.
• I have tried a different browser to see if it is related to my browser.
• I have tried reproducing the issue in safe mode to rule out problems with unsupported custom resources.

Describe the issue you are experiencing

When HA is running in a safe mode, after F5 a "HA is running in a safe mode" popup is shown.
When this popup appears, it may show horizontal lines & a right scrollbar during a transition.
It is clearly seen in FF 135.0.1 & dark theme:

The effect is almost not visible in a light theme & in Chrome 134.0.6998.36 .

Describe the behavior you expected

No ugly transitional effects.

Steps to reproduce the issue

1. Restart in Safe mode.
2. Press F5.

What version of Home Assistant Core has the issue?

2025.3.0b4

What was the last working version of Home Assistant Core?

No response

In which browser are you experiencing the issue?

FF 135.0.1

Which operating system are you using to run this browser?

Win10x64

State of relevant entities

Problem-relevant frontend configuration

Javascript errors shown in your browser console/inspector

Additional information

No response

[ildar170975]

I believed that this could be a common thing with any popups, but failed to reproduce same imperfection with some other popups like this one: