WebResponseStream might be code in Mono choking on something the web server responded with to the Duplicati http report that runs after the backup is done. Do all the systems have this set up the same way?
C:\Program Files\Duplicati 2>Duplicati.CommandLine.exe help sendhttp
HTTP report module (sendhttp):
This module provides support for sending status reports via HTTP messages
Module is loaded automatically, use --disable-module to prevent this
Supported options:
--send-http-url (String): HTTP report url
HTTP report url
--send-http-message (String): The message template
This value can be a filename. If the file exists, the file contents will
be used as the message.
In the message, certain tokens are
replaced:
%OPERATIONNAME% - The name of the operation, normally
"Backup"
%REMOTEURL% - Remote server url
%LOCALPATH% - The path to the
local files or folders involved in the operation (if any)
%PARSEDRESULT%
- The parsed result, if the operation is a backup. Possible values are:
Error, Warning, Success
All command line options are also reported
within %value%, e.g. %volsize%. Any unknown/unset value is removed.
* default value: Duplicati %OPERATIONNAME% report for
%backup-name%
%RESULT%
--send-http-message-parameter-name (String): The name of the parameter to
send the message as
The name of the parameter to send the message as.
* default value: message
--send-http-extra-parameters (String): Extra parameters to add to the http
message
Extra parameters to add to the http message. I.e.
"parameter1=value1¶meter2=value2"
--send-http-level (Enumeration): The messages to send
You can specify one of "Success", "Warning", "Error", "Fatal".
You can
supply multiple options with a comma separator, e.g. "Success,Warning".
The special value "All" is a shorthand for "Success,Warning,Error,Fatal"
and will cause all backup operations to send a message.
* values: Unknown, Success, Warning, Error, Fatal, All
* default value: all
--send-http-any-operation (Boolean): Send messages for all operations
By default, messages will only be sent after a Backup operation. Use this
option to send messages for all operations
--send-http-verb (String): Sets the HTTP verb to use
Use this option to change the default HTTP verb used to submit a report
* default value: POST
--send-http-log-level (Enumeration): Defines a log level for messages
Use this option to set the log level for messages to include in the report
* values: ExplicitOnly, Profiling, Verbose, Retry, Information, DryRun,
Warning, Error
* default value: Warning
--send-http-log-filter (String): Log message filter
Use this option to set a filter expression that defines what options are
included in the report
--send-http-max-log-lines (Integer): Limits log lines
Use this option to set the maximum number of log lines to include in the
report. Zero or negative values means unlimited.
* default value: 100
--send-http-result-output-format (Enumeration): Selects the output format
for results
Selects the output format for results. Available formats: Duplicati, Json
* values: Duplicati, Json
* default value: Duplicati
C:\Program Files\Duplicati 2>
To see what’s in the http report (in case it matters), you could try sending a similar report using email instead. Also possible is that the web server you send to will have some log of what came in, or what error was sent…
There’s also a chance you’ll have more Duplicati information if you increase the log level, e.g. to Information, however it’s also possible that things are upset enough that they can only throw that exception, and no more.