Can't load installation with variable set in its DataModel

Getting this when loading installation file with variable set in its DataModel:

16:43:07.281 ERROR - Fatal error on installation load {thread: AWT-EventQueue-1 , loggerClass: com.ur.view.polyscope.persistence.installation.RobotInstallationPersistence$SerializePersistenceStrategy}
com.thoughtworks.xstream.converters.ConversionException: interface com.ur.view.variables.core.Variable: Cannot find class com.ur.view.variables.core.Variable : Cannot find class com.ur.view.variables.core.Variable
---- Debugging information ----
message             : Cannot find class com.ur.view.variables.core.Variable
cause-exception     : com.thoughtworks.xstream.converters.reflection.ObjectAccessException
cause-message       : Cannot find class com.ur.view.variables.core.Variable
class               : com.ur.view.variables.core.Variable
required-type       : com.ur.view.variables.core.Variable
path                : /Installation/Contributions/URCaps/Contributed[3]/Variable/variable
line number         : 247
------------------------------- : interface com.ur.view.variables.core.Variable: Cannot find class com.ur.view.variables.core.Variable : Cannot find class com.ur.view.variables.core.Variable
---- Debugging information ----
message             : Cannot find class com.ur.view.variables.core.Variable
cause-exception     : com.thoughtworks.xstream.converters.reflection.ObjectAccessException
cause-message       : Cannot find class com.ur.view.variables.core.Variable
class               : com.ur.view.variables.core.Variable
required-type       : com.ur.view.variables.core.Variable
path                : /Installation/Contributions/URCaps/Contributed[3]/Variable/variable
line number         : 247
-------------------------------
message             : interface com.ur.view.variables.core.Variable: Cannot find class com.ur.view.variables.core.Variable : Cannot find class com.ur.view.variables.core.Variable
---- Debugging information ----
message             : Cannot find class com.ur.view.variables.core.Variable
cause-exception     : com.thoughtworks.xstream.converters.reflection.ObjectAccessException
cause-message       : Cannot find class com.ur.view.variables.core.Variable
class               : com.ur.view.variables.core.Variable
required-type       : com.ur.view.variables.core.Variable
path                : /Installation/Contributions/URCaps/Contributed[3]/Variable/variable
line number         : 247
-------------------------------
cause-exception     : com.ur.polyscope.persistence.UnableToConvertValue
cause-message       : interface com.ur.view.variables.core.Variable: Cannot find class com.ur.view.variables.core.Variable : Cannot find class com.ur.view.variables.core.Variable
---- Debugging information ----
message             : Cannot find class com.ur.view.variables.core.Variable
cause-exception     : com.thoughtworks.xstream.converters.reflection.ObjectAccessException
cause-message       : Cannot find class com.ur.view.variables.core.Variable
class               : com.ur.view.variables.core.Variable
required-type       : com.ur.view.variables.core.Variable
path                : /Installation/Contributions/URCaps/Contributed[3]/Variable/variable
line number         : 247
-------------------------------
class               : com.ur.polyscope.installation.Installation
required-type       : com.ur.view.variables.core.Variable
path                : /Installation/Contributions/URCaps/Contributed[3]/Variable/variable
line number         : 247
-------------------------------

Using ur-sdk 1.13.0 and ursim 5.12.4.

Similar problem to Error while starting PolyScope at "com.ur.urcap.conveyortracking [79]" - #2 by urcaps.lorenscheit
Wonder if this has been addressed.