I have one of those too.
Not too familiar with mining/ staking, but I consider them to be orphans. You did stake them, but they are not valid due to another block overruling these in some way or another.
Please correct me if I'm wrong; no techie here.
Yes, that is correct. Everyone competes for staking, sometimes two wallets stake at almost the same time, so one loses out. Like with mining, this can especially happen if your internet connection is slow.