Scrolling skips in discover when using Firefox

[nemhods]

Kibana version: 7.6

Elasticsearch version: 7.6

Browser version: Firefox 73.0.1

Browser OS version: Windows 10

Describe the bug: When scrolling through Discover, the viewport jumps around, making smooth scrolling and skimming through information impossible.

Steps to reproduce:

1. Install ELK stack
2. Load Sample Dataset (e.g. eCommerce)
3. Go to discover, choose timeframe with lots of events (>1000) unfold an event and scroll down (using Firefox)
4. Compare to other browsers that don't exhibit this behavior

Expected behavior: Scrolling is smooth as in other browsers

Screenshots (if relevant):

Looks like something related to infinite scrolling or some mechanism like that.

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[myasonik]

Not a very immediate solution but eventually it'll be resolved whenever #51531 lands

[myasonik]

Didn't mean to close it in case someone else wants to fix it before the big refactor lands

[andrewkcarter]

Any hints on what needs to be fixed? This is plaguing us in 7.6.2, and I tested 7.7.0 and see it there as well.

[andrewkcarter]

In my testing, this issue starts in 7.4.2. And interestingly, it's present in the official docker images (docker.elastic.co/kibana/kibana:7.6.2) but when testing an ElasticCloud hosted 7.6.2 Kibana I cannot reproduce the issue. (edit: I can reproduce there too)

[andrewkcarter]

We've found this CSS will resolve the issue for us @myasonik.

@-moz-document url-prefix() {
    .euiBody-hasPortalContent {
        position: static !important;
    }
}

[kertal]

Just confirmed, it was fixed with #70243, tested in cloud, could reproduce with 7.8.1, but not in 7.9.0 with contains the new EUI version