Why is my garmin R50 deleting my downloaded courses?

I’ve been noticing when I log into my R50 that sometimes I have to redownload a course that I know I had previously downloaded and played. Today I logged in and I only had 1 downloaded course.. I would say previously I had 10-15 courses downloaded. Is it because maybe those courses had updates? I don’t always have wifi to my r50 so kind of annoying trying to download courses repeatedly.