"&-n-b-s-p-;‌" not working

Our agency has created email templates, and used the "&-n-b-s-p-;‌" hack to space the unwanted content from the preheader.

However, we have noticed when we tested this in Litmus, that it was changing the "&-n-b-s-p-; " into text “&n bsp;” hence making a strange “&n bsp;” display in the preheader.

Is there away around this? Or has anyone else had this issue?

Thanks