VxRail: Uploading the upgrade bundle fails with no error

• During the upload of an upgrade bundle, the upload is stuck (usually at 37% but may vary)
• After a while the bar of uploading disappears from the GUI and no error is displayed either in the GUI of the lcm.log
• Customer might have proxy enabled or might be accessing VxRail from jump server not on the VxRail network

The web.log (/var/log/mystic/web.log) may show:

2019-06-26T06:59:39.064+0000 ERROR [tomcat-http--48] com.emc.mystic.manager.web.webutil.RestErrorHandler RestErrorHandler.handleExceptionInternal:211 - Get REST error: error code=201, http status code=422, message=Authentication could not be completed due to network connectivity problems.
2019-06-26T06:59:07.496+0000 ERROR [tomcat-http--13] com.emc.mystic.manager.web.webutil.RestErrorHandler RestErrorHandler.handleExceptionInternal:210 - Handlingexception for request ServletWebRequest: uri=/extension/mystic/virtualAppliance/1/upgradePkg/upload;client=192.168.10.148;session=8BF1D54DAC0B453DFF941E62141C1B69;user=administrator@vsphere.local
org.springframework.web.multipart.MultipartException: Failed to parse multipart servlet request; nested exception is org.apache.commons.fileupload.FileUploadBase$IOFileUploadException: Processing of multipart/form-data request failed. null
        at org.springframework.web.multipart.commons.CommonsMultipartResolver.parseRequest(CommonsMultipartResolver.java:168) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]

• If the customer is using a jump server to access VxRail Manager not on the same network, please ask them to access from a device on the same network
• If a proxy is enabled on VxRail Manager, disable it: Cluster level > Configure > Settings