Odd behaviour - the beeping incident

Have had the system for a month now with no real issues.  Last night with the system set in HOME mode after an hour or so we were woken by the base station beeping relatively quietly but constantly.  No alarm had been triggered.  Turned the system off and noticed that the simplicam video that is produced when the system is disarmed had not recorded and was showing as unavailable.  

Have had it set in HOME mode for some time today and everything seems to be back to normal.  Can't find any info on what this is - don't think it's a battery in a sensor because I think the system records that?

Anyone have any ideas what happened?  Could it be something to do with the simplicam?