Community PR provided: https://github.com/camunda/camunda-external-task-client-java/pull/103

Copied from the PR description:

If a file variable is passed to a ExternalTask as inputParameter (local variable) loading the variable value fails because the variable is not present in result of query /execution/<PROCESS_INSTANCE_ID>/localVariables/<NAME>/data. (It is however present in /execution/<EXECUTION_ID>/localVariables/<NAME>/data but the global variables are missing here...)

I fixed this by using /variable-instance endpoint where all variables both local and global are present. From this endpoint I first load the variable's ID and than load the data by calling /variable-instance/<VARIABLE_ID>/data. This solution consists of two API requests but I don't think this could be done in a single request because in fetchAndLock there is no data based on which we could differentiate whether the variable is local or global.