I have this message and could not find information about what it is.
Can anyone tell me what it is?
Have you set PREARM_CHECKS to 1 ? You should.
It could be the flight controller had previously locked up or crashed (in software/computer terms) and it is indicating there is a crashdump file recorded for diagnostics.
You can download it via Mavftp or pull the SD Card to get it.
Upload it to a filesharing site and post a link to it so we can see what’s going on.
Specify what flight controller you have, and anything unusual that might have happened.