Memory leaks detected in Kotlin/Native framework when using callback function in iOS development

I develop a K/N Multiplatform module and using the latest Kotlin 1.4.21. I found it often shows the following error message and terminate the app (crash) when I deinit this object:

Memory leaks detected, x objects leaked!
Use `Platform.isMemoryLeakCheckerActive = false` to avoid this check.

I cannot not figure out the reason of the memory leak, and following is my kotlin class using callback function:

class Detector(private val onEventDetected: ((event: Event) -> Unit)?) {

    fun processData(data: Data) {
        detectEvent(data)
    }

    private fun detectEvent(data: Data) {
        if (...) {
            ... // some logic
            onEventDetected?.invoke(event)
        }
    }
}

I found when I comment out the onEventDetected?.invoke(event), the error message got disappear. How can I implement the class to forbidden the memory leak issue?

Updated: Dec 21, 2020

I add WeakReference for different platforms:

// Common module
expect class WeakReference<T : Any>(referred: T) {
    fun clear()
    fun get(): T?
}
// For JVM
actual typealias WeakReference<T> = java.lang.ref.WeakReference<T>

// For iOS Native
actual typealias WeakReference<T> = kotlin.native.ref.WeakReference<T>

And update the class:

class Detector(private val onEventDetected: ((event: WeakReference<Event>) -> Unit)?) {

    fun processData(data: Data) {
        detectEvent(data)
    }

    private fun detectEvent(data: Data) {
        if (...) {
            ... // some logic
            onEventDetected?.invoke(WeakReference(event))
        }
    }
}

But the Memory leaks detected issues still happened. There is no clue to solve this problem :(