3011131 - SAP Cloud Connector, on-premise system is not reachable, Write operation failed for payload message

The SAP Cloud Connector connection to an on-premise system fails with a "write operation failed for payload message" ERROR message (ljs_trace.log):

#ERROR#com.sap.core.connectivity.spi.processing.AbstractProtocolProcessor#tunnel-client-76-1#0x377e6427#Write operation FAILED for payload message packet with size 4,537 for client channel [id: 0xb49402ee, L:/10.10.1.1:62032 - R:mybackend.local/10.10.1.2:50001]. Cause: javax.net.ssl.SSLException: SSLEngine closed already|

When Cloud Connector Loggers is set to ALL or Debug some additional information is logged with DEBUG severity level:

#DEBUG#com.sap.core.connectivity.spi.processing.OutboundConnectionErrorHandler#tunnel-client-76-1#0x377e6427#Protocol processing error:
com.sap.core.connectivity.protocol.http.handlers.HttpProtocolException: javax.net.ssl.SSLHandshakeException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at com.sap.core.connectivity.protocol.http.handlers.HttpProtocolClientCodec.exceptionCaught(HttpProtocolClientCodec.java:80)
at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:302)

SAP Cloud Connector

SSLException, SSLEngine, SunCertPathBuilderException, PKIX, Write operation failed for payload message
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