Download sermon only works some times.

I am having a problem with some of the sermons on my site. About half of the sermons uploaded in the last 6 months, the download only grabs an image and not the the sermon. They stream fine but I cannot get it to download the file. I have checked all permissions and everything is ok. Any help?
Here is an example
Not Working
And 1 from the same site that works
Working

One thing could be the memory limit of PHP. If the limit is set to like 20M the first sermon would fail while the second work.
You can check this setting in the Joomla System Information.
Also, the server error log would have a fatal error entry in this case.

You could ask your hoster to raise the memory limit, or you could make the files smaller.

Ok I checked the download limit. Server said its unlimited. System info is set at 95M. Most sermons are around 20-25M. I uploaded a 90M audio file and it downloads fine from the website. Any more suggestions?

Also the latest sermon will not download. When I use Internet Download Manager in chrome, clicking on the "download sermon" link IDM just hangs and doesn't download anything. IDM has a tab that shows "download audio from this site". When I click on that it works and downloads the sermon from the site.

I'd rename folders and files to remove spaces and any special characters. use underscore for spaces '_'.

Maybe also check if there are any errors in the server error log.

I just tried that and it still doesn't work. I tried going in to file on my computer and applying all permissions to it. Renamed 3 different names (using _ for each space, and no spaces, and a random name)and none of this worked. The sermon still behaves the same.