Intermittant motion video recording on only one of three cameras

We are getting intermittent Motion Recordings on one of our three security cameras. Some of the Motion triggered videos are OK while some show up as "inaccessible" on my phone. When I look at these videos while logged in to the web account, they just look black. Person videos are all OK. I don't see this at all on my other two cameras or the doorbell cam. What could cause this? How can I fix it?