Why the resolution of the client produce will decrease after a period of time

Hi everyone,have you seen anything like this? is there any way to fix it? thanks
At first

Two minutes later

then ,never come back !

I use fixed resolution 720p to init client camera produce

async produce(type, deviceId = null) {
        let mediaConstraints = {}
        let audio = false
        let screen = false
        switch (type) {
            case mediaType.audio:
                mediaConstraints = {
                    audio: {
                        deviceId: deviceId
                    },
                    video: false
                }
                audio = true
                break
            case mediaType.video:
                mediaConstraints = {
                    audio: false,
                    video: {
                        width: 1280,
                        height: 720,
                        deviceId: deviceId
                        /*aspectRatio: {
                            ideal: 1.7777777778
                        }*/
                    }
                }
                break
            case mediaType.screen:
                mediaConstraints = false
                screen = true
                break;
            default:
                return
                break;
        }

Browser can decrease resolution due to CPU or bandwidth restrictions. Open dev tools available in the browser and debug it there, it should tell you precisely what is going on and why.