IMDB List Technical Issue

One of my IMDB lists had a change where  out of nowhere hundreds of film titles went missing and my titles were placed out of the manual order I put them in. The change happened right as I was managing my list. This is the first time this has ever happened to me since I started using the site to manage my content for the past few years. I want to know why this may have happened. Before the issue my list had a little over a thousand film titles. Now it has around little less than eight hundred. I can't change the order to what it was as I ordered my list manually instead of the order options given. 

Is there a way to maybe prevent this from happening in the future. I will look to save my lists on a regular basis by exporting them. Besides that  is there any thing else anyone can recommend? I use the IMDB website on Safari mostly through my Apple MacBook Air.