3400424 - While SUM upgrade of AS Java, deployment of UI5 component takes too long or fails - DeploymentException: Operation [deploy] of [sap.com_sapui5<...>] failed

In the Execution phase of the AS Java upgrade the deployment of UI5 SCA takes long time or hangs forever. SUM logs show:

[...]
ERROR CODE DPL.DCAPI.1023] DCNotAvailableException
.Reason: [ERROR CODE DPL.DC.3218] Deploy controller is not ready to serve yet. Probably a un/deploy operation after offline phase is in progress at the moment.
[...]

Thread dumps with MMC snapshot show hanging thread:

[...]
Thread 'DeployThread[sap.com_ui~five]', process 'server0', index '<...>'
"DeployThread[sap.com_ui~five]"
[...]

deploy.0.trc might show various exceptions with the beginning:

[…]
com.sap.engine.services.dc.cm.deploy.DeploymentException: ASJ.dpl_dc.001085 Operation [deploy] of [sap.com_sapui5<...>] failed
[…]

defaultTrace might show various exceptions like:

[...]
java.io.FileNotFoundException: /usr/sap/<SID>/<instnr>/j2ee/cluster/apps/sap.com/ui~five/servlet_jsp/sapui5-1.52/root/WEB-INF/lib/sap.ui.server.abap-1.52.51.jar
[...]

std_server0.out show online deployment for very long time:

[...]
Startup mode [SAFE] and action [DEPLOY] read
WARNING: The server process is in SAFE mode. No applications will be started
[...]

Process is very slow, checks in command line / browser / etc. show various entries for hours like:

[...]
==== PROGRESS START =====
[...]
Deploying [sap.com_ui~five (sda)] ...
[...]
Thread Dump:  Browser with Sum: <xx>% Deploying Component ui~five
[...]
SUM  changes the screnn: Deploying component ui~five
[...]

1. SAP NetWeaver Application Server Java 7.50
2. Software Update Manager (SUM) SP upgrade

sapui5, ui~five, ui five, ui5, sap.com_ui~five, Software Update Manager, SUM, upgrade, deploying, ui5 , KBA , BC-JAS-DPL , Deployment , BC-UPG-TLS-TLJ , Upgrade tools for Java , CA-UI5-COR , Core and Runtime , Problem