InvokeHTTP randomly hangs

I have a NiFi flow [on a 2 processor machine using 8/5 thread counts] where the InvokeHTTP block is no longer processing files from the queue [shown below]:

As you can see there are 8 processes running but these seem to be stuck for hours and the only way out of it is manually stopping and terminating the block. This results in the following log message:

2020-05-18 08:31:06,228 ERROR [Timer-Driven Process Thread-12 <Terminated Task>] o.a.nifi.processors.standard.InvokeHTTP InvokeHTTP[id=f2f13d29-016b-1000-293d-c0cb04835881] Routing to Failure due to exception: java.net.SocketTimeoutException: timeout: java.net.SocketTimeoutException: timeout
java.net.SocketTimeoutException: timeout
	at okhttp3.internal.http2.Http2Stream$StreamTimeout.newTimeoutException(Http2Stream.java:593)
	at okhttp3.internal.http2.Http2Stream$StreamTimeout.exitAndThrowIfTimedOut(Http2Stream.java:601)
	at okhttp3.internal.http2.Http2Stream.takeResponseHeaders(Http2Stream.java:146)
	at okhttp3.internal.http2.Http2Codec.readResponseHeaders(Http2Codec.java:120)
	at okhttp3.internal.http.CallServerInterceptor.intercept(CallServerInterceptor.java:75)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
	at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:45)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)
	at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)
	at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
	at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:120)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)
	at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:185)
	at okhttp3.RealCall.execute(RealCall.java:69)
	at org.apache.nifi.processors.standard.InvokeHTTP.onTrigger(InvokeHTTP.java:791)
	at org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27)
	at org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1162)
	at org.apache.nifi.controller.tasks.ConnectableTask.invoke(ConnectableTask.java:209)
	at org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:117)
	at org.apache.nifi.engine.FlowEngine$2.run(FlowEngine.java:110)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

 
Before stopping the process, I had a look into the nifi-bootstrap.log file and noticed a number of similar messages. I'm not sure whether these are related since no direct reference to InvokeHTTP is made.

"NiFi Web Server-556239" Id=556239 TIMED_WAITING  on java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject@2f7a83f7
	at sun.misc.Unsafe.park(Native Method)
	at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
	at org.eclipse.jetty.util.BlockingArrayQueue.poll(BlockingArrayQueue.java:392)
	at org.eclipse.jetty.util.thread.QueuedThreadPool.idleJobPoll(QueuedThreadPool.java:653)
	at org.eclipse.jetty.util.thread.QueuedThreadPool.access$800(QueuedThreadPool.java:48)
	at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:717)
	at java.lang.Thread.run(Thread.java:748)

"OkHttp ConnectionPool" Id=213155 TIMED_WAITING  on okhttp3.ConnectionPool@72d6189
	at java.lang.Object.wait(Native Method)
	at java.lang.Object.wait(Object.java:460)
	at okhttp3.ConnectionPool$1.run(ConnectionPool.java:67)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
	Number of Locked Synchronizers: 1
	- java.util.concurrent.ThreadPoolExecutor$Worker@7b6a1485

"Okio Watchdog" Id=556238 TIMED_WAITING  on java.lang.Class@2b4512c0
	at java.lang.Object.wait(Native Method)
	at java.lang.Object.wait(Object.java:460)
	at okio.AsyncTimeout.awaitTimeout(AsyncTimeout.java:361)
	at okio.AsyncTimeout$Watchdog.run(AsyncTimeout.java:312)

Any help/insights on this would be greatly appreciated.