Display Template Error

I'm working in SharePoint 2013 and I've customised a display template to show a library of images and some text.  Upon clicking the thumbnail, I want the image to download, as opposed to open in a new tab or open the image in the library.

So I changed the script from:

<div class="zoom-pictureOnTopImageContainer" id="_#= pictureContainerId =#_">
            <a class="cbs-pictureImgLink" href="_#= linkURL =#_" title="_#= $htmlEncode(line1) =#_" id="_#= pictureLinkId =#_">_#= pictureMarkup =#_      

To:

<a class="cbs-pictureImgLink" href="_#= linkURL =#_" title="_#= $htmlEncode(line1) =#_" id="_#= pictureLinkId =#_" download="_#= pictureURL =#_">_#= pictureMarkup =#_

So I added download="_#= pictureURL =#_" which I thought would mean the image would download and the name would be the picture URL.

It works great for me and I was very happy. So I published my new display template and now my users just get Something Went Wrong where the display template should be.

If I take the download part out, the template works again for my users. I could understand if it didn't work at all, but as an administrator, it works for me, just not my users - very strange.

To add, just in case it's not obvious 🙂 I'm still a newbie with SharePoint, but have HTML experience  and it's driving me insane trying to work it out what the problem is, so please help