Timer Task suspend when device going to sleep

Question

I'm developing timer app like focus to do and to achieve this I used a foreground service and timer task within it.

now when when device is screen off timer task no longer emitted.

and after a little when device screen turns on timer task emits immediately

my timer interval is set to 100 ms, but updating the UI every 1 second. Also the app was excluded from battery saving.

my custom timer task class:

     abstract class CustomTimer @JvmOverloads constructor(
     private val totalTime: Long,
     private val interval: Long,
     private val delay: Long = 0
     ) :
Timer("PreciseCountdownTimer", true) {
private var task: TimerTask
private var startTime: Long = -1
private var timeLeft: Long = 0
private var restart = false
private var wasCancelled = false
private var isDisposed = false
private var wasStarted = false

init {
    task = buildTask(totalTime)
    isDisposed = false
}

private fun buildTask(totalTime: Long): TimerTask {
    return object : TimerTask() {
        override fun run() {
            if (startTime < 0 || restart) {
                startTime = scheduledExecutionTime()
                timeLeft = totalTime
                restart = false
            } else {
                timeLeft = totalTime - (scheduledExecutionTime() - startTime)
                if (timeLeft <= 0) {
                    this.cancel()
                    wasCancelled = true
                    startTime = -1
                    Log.d("shower", "run: ")
                    onFinished()
                    return
                }
            }

            onTick(timeLeft)
        }
    }
}

fun getTimeLeft() = timeLeft
fun start() {
    wasStarted = true
    isDisposed = false
    this.scheduleAtFixedRate(task, delay, interval)
}

fun stop() {
    wasCancelled = true
    task.cancel()
    onStop()
}

fun restart() {
    if (!wasStarted) {
        start()
    } else if (wasCancelled) {
        wasCancelled = false
        task = buildTask(totalTime)
        start()
    } else {
        restart = true
    }
}


fun isDisposed() = isDisposed
fun pause() {
    wasCancelled = true
    task.cancel()
    onPaused()
}

fun updateWithNewTime(time : Long){
    task.cancel()
    task = buildTask(time)
    startTime = -1
    start()
}

fun resume() {
    wasCancelled = false
    isDisposed = false
    task = buildTask(timeLeft)
    startTime = -1
    start()
    onResumed()
}

// Call this when there's no further use for this timer
fun dispose() {
    this.cancel()
    this.purge()
    isDisposed = true
}

abstract fun onTick(timeLeft: Long)
abstract fun onFinished()
abstract fun onPaused()
abstract fun onResumed()
abstract fun onStop()

}

I created log file which prove my assertion to timer not working in sleep mode. It is not emitted from second 3 until second 16 and then emits very fast in second 16 and 17... log is updated every 1 second.