hivemq-mqtt-client: NoClassDefFoundError in Android 5-6 when built in Android Studio 4.2.1

Expected behavior

MQTT Client can init and connect with Android 5-6 devices

Actual behavior

The client is crashing in Android 5 and Android 6 with

java.lang.NoClassDefFoundError: com.hivemq.client.internal.mqtt.-$$Lambda$QT9XFB_2yV951PYVP80Cqx3qU9Q
	at com.hivemq.client.internal.mqtt.MqttRxClientBuilderBase.automaticReconnect(MqttRxClientBuilderBase.java:156)
	at com.hivemq.client.internal.mqtt.mqtt3.Mqtt3RxClientViewBuilder.automaticReconnect(Mqtt3RxClientViewBuilder.java:38)
	at com.mypackage.MqttHiveClient.<init>(MqttHiveClient.java:54)

No issues with newer Android versions or when built in Android Studio 4.1.x

To Reproduce

Run the app with following code

Reproducer code

                Mqtt3ClientBuilder mqtt3ClientBuilder = Mqtt3Client.builder()
                        .identifier(identifier)
                        .serverHost(host)
                        .serverPort(port)
                        .simpleAuth(Mqtt3SimpleAuth.builder()
                                .username(username)
                                .password(password.getBytes())
                                .build())
                        .automaticReconnect()
                        .initialDelay(10, TimeUnit.SECONDS)
                        .maxDelay(60, TimeUnit.SECONDS)
                        .applyAutomaticReconnect();

dependencies:

    implementation 'com.hivemq:hivemq-mqtt-client:1.2.2'
    implementation 'com.hivemq:hivemq-mqtt-client-websocket:1.2.2'
    implementation 'net.sourceforge.streamsupport:android-retrostreams:1.7.3'
    implementation 'net.sourceforge.streamsupport:android-retrofuture:1.7.3'

buildscript/dependencies:

        classpath 'com.android.tools.build:gradle:4.2.1'
        classpath 'com.github.dcendents:android-maven-gradle-plugin:1.4.1'
        classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.8.5'
        classpath 'gradle.plugin.com.github.sgtsilvio.gradle:android-retrofix:0.3.6'

apply plugin: 'com.github.sgtsilvio.gradle.android-retrofix'