strange scrolling behaviour on v1.11.0

[sweetp]

I have this strange issue, with my custom persona child theme activated:
https://cl.ly/46197b3a678b

where should I look to debug this?

[sweetp]

there's something causing it in my custom css...
ill track it down

[sweetp]

here was the offending line:

body {
  height: 100%;
}