Timeline goes blank after jumping to first unread a couple weeks back and then scrolling down

[MadLittleMods]

Steps to reproduce

1. Have a room with many unreads
2. Click the "Jump to first unread message." ^ up-arrow
3. Scroll down
4. At a certain point, the timeline just goes blank with no scroll

Outcome

What did you expect?

The timeline continues infinite scrolling like normal

What happened instead?

The timeline just goes completely blank and doesn't recover. Sometimes it can recover and loads again but at slightly different place.

I've reproduced with and without a poll in the mix.

Dev notes

Can we add a way to enable DEBUG_SCROLL for the ScrollPanel without having to rebuild the app with the boolean changed to true? I just want to enable logs for what I am looking at in the devtools console after the app is deployed and running.

Created #21532 to track this separately ⏩

Operating system

Windows 10

Browser information

Chrome Version 99.0.4844.74

URL for webapp

develop.element.io

Application version

585b651b4c0e-react-8cd805ad2317-js-75674d961a15 and 269ec4609ade-react-ebbda285ca6a-js-a6fe8797f0b0

Homeserver

matrix.org

Will you send logs?

Yes

Rageshake logs:

• https://github.com/matrix-org/element-web-rageshakes/issues/11610
• https://github.com/matrix-org/element-web-rageshakes/issues/11627

Seems related/correlated to a bunch of these type of log lines:

• Discarding an event, we don't have a call/peerConn m.room.encrypted
• Discarding an event, we don't have a call/peerConn org.matrix.msc3381.poll.response

[t3chguy]

This is an extreme case of #21432

[MadLittleMods]

@t3chguy It seems different unless the logs are showing the same thing to you?

In my case, I jump back a couple weeks. Then I scroll down (not up) catching up on messages for a little bit. Then out of nowhere, the whole timeline goes completely blank (no messages) and doesn't recover at all. I've had this happen multiple times now.

[t3chguy]

Rageshakes on that issue have the same logs you identified:

2022-03-16T10:05:53.071Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.071Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.071Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.071Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.072Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.072Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.072Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.072Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.072Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.072Z W Discarding an event, we don't have a call/peerConn m.room.message
2022-03-16T10:05:53.073Z W Discarding an event, we don't have a call/peerConn m.room.message

[t3chguy]

and doesn't recover at all

The recovery may require events to be in the timeline.

[MadLittleMods]

Thanks @t3chguy ⏩