Could you please reply back on your other thread Unscheduled backup so others reading the thread can benefit from whatever the solution was? Thanks.

About this one, please let us know the DP version and platform, so we can double check this is possibly not a known issue. Besides that, if a service is going down then it's always a good idea to check system logs. In case of a crash there's most likely something logged there. I would also check debug.log (ProgramData\OmniBack\log or /var/opt/omni/log) in case of the mmd going down. If all that is not helping and the issue occurs more often then you may need to run mmd in debug mode.

DP version - 10.91

Platform- windows and linux

So is your cell server Windows or Linux? Anything found in any logs?

Please be aware 10.91 is at end of support this month.

Found error in debug.log

2024-03-11 17:21:48 MMD.5505.43526396 ["/sm/smcmn/smmain.c $Rev$ $Date::]

Session failed during initialization - panic mode

Is it any dependency on NTP server? 

So this was on March, 11. I assume this is when services were (re)started!? Do you see multiple entries like that or really just one only? If the problem is reproducible then you may want to start the mmd with debugs and provide those to support. If you see just 1 entry like this in debug.log then I guess you will never know what happened.

Why do you think this may be related to ntp?

In debug log single entry of 11th Mar 2024.Before this rest entry are 2023.From 11th mar backup is failing.

I'm thinking about NTP because NTP not synchronized, When I see mmd down. 

If this was only seen once recently then it is probably difficult to reproduce. You could still check system logs for messages around the same time though.