The javascript for "copy values to all rows" (copyValues function) fails with a javascript error when used on a profile containing a custom data field that has multiple checkboxes.

copyValues defined in templates/CRM/Contact/Form/Task/BatchUpdateProfile.tpl assumes the presence of a field with a name like "field[1234][custom_12]" for a contact_id 1234 and a multi-checkbox field which is custom_12. This fails with an error if the multi checkbox fields are "red", "blue", "green" then the field names will be "field[1234][custom_12][red]", etc.

One fix is to scan the first row of the table for inputs with a partial name match against "field[1234][custom_12]", then iterate through the matching inputs and copy values from there.

See also CRM-1554 (similar but relates to date fields)