Stream2JSON errors - How to debug?

I have these errors in the log but I don’t know what’s causing them:

2021-06-03 19:35:14.771 [ERROR] [rg.apache.cxf.jaxrs.utils.JAXRSUtils] - Problem with writing the data, class org.openhab.core.io.rest.Stream2JSONInputStream, ContentType: application/json
2021-06-03 19:35:14.812 [ERROR] [internal.JSONResponseExceptionMapper] - Unexpected exception occurred while processing REST request.
java.io.IOException: Close SendCallback@13dea21[PROCESSING][i=null,cb=org.eclipse.jetty.server.HttpChannel$SendCallback@3c6d6e2f] in state PROCESSING
	at org.eclipse.jetty.util.IteratingCallback.close(IteratingCallback.java:428) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.server.HttpConnection.onClose(HttpConnection.java:519) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.io.ssl.SslConnection.onClose(SslConnection.java:363) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.io.SelectorManager.connectionClosed(SelectorManager.java:345) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.io.ManagedSelector$DestroyEndPoint.run(ManagedSelector.java:1104) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:882) [bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1036) [bundleFile:9.4.40.v20210413]
	at java.lang.Thread.run(Thread.java:834) [?:?]
2021-06-03 22:15:16.676 [ERROR] [rg.apache.cxf.jaxrs.utils.JAXRSUtils] - Problem with writing the data, class org.openhab.core.io.rest.Stream2JSONInputStream, ContentType: application/json
2021-06-03 22:15:16.678 [ERROR] [internal.JSONResponseExceptionMapper] - Unexpected exception occurred while processing REST request.
java.io.IOException: Close SendCallback@55c06b3e[PROCESSING][i=null,cb=org.eclipse.jetty.server.HttpChannel$SendCallback@10c2ffe2] in state PROCESSING
	at org.eclipse.jetty.util.IteratingCallback.close(IteratingCallback.java:428) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.server.HttpConnection.onClose(HttpConnection.java:519) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.io.ssl.SslConnection.onClose(SslConnection.java:363) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.io.SelectorManager.connectionClosed(SelectorManager.java:345) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.io.ManagedSelector$DestroyEndPoint.run(ManagedSelector.java:1104) ~[bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:882) [bundleFile:9.4.40.v20210413]
	at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1036) [bundleFile:9.4.40.v20210413]
	at java.lang.Thread.run(Thread.java:834) [?:?]

They appear randomly and seem to affect the Tapo binding, so I’ve tried to disable all my Tapo things. But the errors continued, so I’ve installed a mqtt logger but I did not find anything suspicious.

How can I debug such situation ? I’m using OH3.1.0.M5

Looks like an important part. REST requests may come from UI … or just about anywhere else (external systems, your own scripts or rules), but not normally from a binding.
It’s not clear to me if it is having trouble handling the incoming request, or in formulating a response i.e. choking on internal OH data like a bad Item definition.

You might close down all UI temporarily and see if it stops.

I have an external script in python that uses REST. I’ll disable it to test if this is the cause. Thanks.