What is the reason of these ‘task manager lost’ errors? I do not see any infra level issues. Has anyone else faced it?

Caused by: org.apache.flink.runtime.io.network.netty.exception.RemoteTransportException: Connecting to remote task manager '/xx.xx.xx.xxx:34387' has failed. This might indicate that the remote task manager has been lost.
	at org.apache.flink.runtime.io.network.netty.PartitionRequestClientFactory.connect(PartitionRequestClientFactory.java:169)
	at org.apache.flink.runtime.io.network.netty.PartitionRequestClientFactory.connectWithRetries(PartitionRequestClientFactory.java:135)
	at org.apache.flink.runtime.io.network.netty.PartitionRequestClientFactory.createPartitionRequestClient(PartitionRequestClientFactory.java:96)
	at org.apache.flink.runtime.io.network.netty.NettyConnectionManager.createPartitionRequestClient(NettyConnectionManager.java:95)
	at org.apache.flink.runtime.io.network.partition.consumer.RemoteInputChannel.requestSubpartition(RemoteInputChannel.java:186)
	... 16 more
Caused by: org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannel$AnnotatedNoRouteToHostException: No route to host: /xx.xx.xx.xxx:34387
Caused by: java.net.NoRouteToHostException: No route to host
	at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
	at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:716)
	at org.apache.flink.shaded.netty4.io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:330)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:334)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:707)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
	at org.apache.flink.shaded.netty4.io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986)
	at org.apache.flink.shaded.netty4.io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	at java.lang.Thread.run(Thread.java:750)