[BUG] issues with simulcast layers

[pnts-se]

Describe the bug
When developing locally, if I join on mobile (ios), and then join with another peer and start webcam, the serverside consumer emits layerschange event with layers set to null.

From Mediasoup documentation: "When there is no available bitrate for this consumer (even for the lowest layers) so the event fires with null as argument" https://mediasoup.org/documentation/v3/mediasoup/api/#consumer-on-layerschange

Perhaps that's the case, but I'm, on high speed wifi so obviously eventually there will be bandwidth. No new layerschange event is emitted.

If I join with a third peer and start the webcam, a new layerschange event is emitted in the consumer and it start. The new consumer for the third peer also works without problems.

To Reproduce
Steps to reproduce the behavior:

1. Join with mobile (ios)
2. Join with another peer and start webcam
3. Watch media-node logs for layerschange event
4. See client-side VideoView doesn't work, it has a spinner.

Expected behavior
If there is no bandwidth, I would expect a new layerschange event to be emitted once there is.

[pnts-se]

I can trigger it to work from mobile (ios) client side by putting peer in fullscreen and holding the phone horizontally. That will trigger a new setConsumerPreferredLayers from room-server to media-node and it will start to work.

This is not only relevant for mobile. I can reproduce the issue on desktop if I have a small enough window when remote peer starts its webcam. See edumeet/edumeet-client#116

[pnts-se]

If I disable simulcast I can't reproduce the issue.

Mediasoup logs when the issue occur:

mediasoup:WARN:Channel [pid:114193] webrtc::ProbeController::Process() | kWaitingForProbingResult: timeout +891ms
  mediasoup:Channel [pid:114193] RTC::Producer::ReceiveRtpPacket() | key frame received [ssrc:585945142, seq:21838] +25ms
  mediasoup:Channel [pid:114193] RTC::Producer::ReceiveRtpPacket() | key frame received [ssrc:3924621829, seq:18106] +0ms
  mediasoup:WARN:Channel [pid:114193] RTC::RtpStreamRecv::OnTimer() | RTP inactivity detected, resetting score to 0 [ssrc:2027180633] +491ms
  mediasoup:Channel [pid:114193] RTC::SimulcastConsumer::UpdateTargetLayers() | target layers changed [spatial:-1, temporal:-1, consumerId:2167bf04-37e6-4be7-b6b6-e4086e16ab22] +1s

Target layers being set to null can happen for a number of reasons.

[pnts-se]

Seems like a lot of changes related to preferred consumer layers seems to be the culprit.
It's very difficult to troubleshoot.
As of now I can only reproduce it on local development environment.

[pnts-se]

I'm absolutely not saying this is a bug in mediasoup, but we can learn from this issue:
versatica/mediasoup#990