string variables in Work item templates do not work

Dear,

when using work items string variables (e.g., ${myvariable}) in the summary of work items, these seem not to be recognized when going to the "Create work items template". The "Next" button is not enabled when it is expected when such a variable is present (after the window wiht "check variable attributes"). When using the Work item template, an error message is issued "Error creating work item set from template fdfsd. The work items were not created. Details: 'Save Work Item' failed. Preconditions have not been met: The 'Summary' attribute needs to be set (work item <02:14:15>).",

kind regards

Paul