Error while inserting a multiple select in an outgoing mail

I know there is a bug when inserting a linked or lookup record in an outgoing mail (with the work around using an extra field with an ArrayJoin formula). But now I encounter such an error while trying to insert a value from a multiple select record (see attached screenshot). This results in an error, just saying that the message of the mail could not be constructed.

Is this a bug or is there something special with a multiple select value? I don’t get it that in the screenshot it suggests ‘Making a new list of’, in stead of looking for the value of the chosen multiple select.