If you see this style of error after upgrading a 7280SE, it’s because EOS past 4.23 doesn’t support the good ol’ 7280SE (reference https://www.arista.com/en/support/advisories-notices/end-of-support/10276-end-of-software-support-for-7500e-7280e):

Jul 27 07:34:34 rtr-lax-int2 SuperServer: 93: %SYS-5-SYSTEM_RESTARTED: System restarted
Jul 27 07:34:34 rtr-lax-int2 SuperServer: 94: %SYS-6-SYSTEM_INFO: Software image version: 4.27.4.1M
Jul 27 07:34:34 rtr-lax-int2 SuperServer: 95: %SYS-6-SYSTEM_INFO: Model: ( unknown )
Jul 27 07:34:34 rtr-lax-int2 SuperServer: 96: %SYS-6-SYSTEM_INFO: Serial number: ( unknown )
Jul 27 07:34:34 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_STARTED: 'LedPolicy' starting with PID=4066 (PPID=2271) -- execing '/usr/bin/LedPolicy'
Jul 27 07:34:36 rtr-lax-int2 LedPolicy: 97: %AGENT-6-INITIALIZED: Agent 'LedPolicy' initialized; pid=4066
Jul 27 07:34:38 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_TERMINATED: 'LedPolicy' (PID=4066, status=134) has terminated.
Jul 27 07:34:38 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_RESTART: Restarting 'LedPolicy' immediately (it had PID=4066)
Jul 27 07:34:38 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_STARTED: 'LedPolicy' starting with PID=4098 (PPID=2271) -- execing '/usr/bin/LedPolicy'
Jul 27 07:34:39 rtr-lax-int2 LedPolicy: 98: %AGENT-6-INITIALIZED: Agent 'LedPolicy' initialized; pid=4098
Jul 27 07:34:41 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_TERMINATED: 'LedPolicy' (PID=4098, status=134) has terminated.
Jul 27 07:34:41 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_RESTART: Restarting 'LedPolicy' immediately (it had PID=4098)
Jul 27 07:34:41 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_STARTED: 'LedPolicy' starting with PID=4120 (PPID=2271) -- execing '/usr/bin/LedPolicy'
Jul 27 07:34:42 rtr-lax-int2 LedPolicy: 99: %AGENT-6-INITIALIZED: Agent 'LedPolicy' initialized; pid=4120
Jul 27 07:34:44 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_TERMINATED: 'LedPolicy' (PID=4120, status=134) has terminated.
Jul 27 07:34:44 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_RESTART: Restarting 'LedPolicy' immediately (it had PID=4120)
Jul 27 07:34:44 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_STARTED: 'LedPolicy' starting with PID=4142 (PPID=2271) -- execing '/usr/bin/LedPolicy'
Jul 27 07:34:45 rtr-lax-int2 LedPolicy: 100: %AGENT-6-INITIALIZED: Agent 'LedPolicy' initialized; pid=4142
Jul 27 07:34:47 rtr-lax-int2 ProcMgr-worker: %PROCMGR-6-PROCESS_TERMINATED: 'LedPolicy' (PID=4142, status=134) has terminated.
Jul 27 07:34:47 rtr-lax-int2 ProcMgr-worker: %PROCMGR-3-PROCESS_DELAYRESTART: 'LedPolicy' (PID=4142) restarted too often! Delaying restart for 120.0 (until 2022-07-27 07:36:47.091950)

So, what you’ll need to do at this point is config update to boot back to your prior EOS version that had been running. If you reload the switch into that version, you’ll probably find the later version altered your config in a bad way. For example, mine lost all my VRF’s, including the management VRF, so good thing I was logged in via serial. What you should do is copy your backup config to the startup config, which will of course include the correct boot statement for the old image since you took the backup before modification correct? Then reload without saving running config.

Or, if you’ve already reloaded and have a broken config, use the configure replace command to fix it:

configure replace flash:/20220726.cfg

Now that you’ve done that, you can upgrade to the latest version of 4.23, currently 4.23.12M which seems to work fine on the DCS-7280SE-68-R models I still have running.

Side note; depending on the EOS version you’re coming from, 4.23 compared to some of the 4.1x range stuff has a much longer interface / mlag activation delay compared to prior releases. So, if your switch is up but seemingly stuck with all its interfaces in an errdisabled state, you may find it spits out an informational notice on the console a few minutes later about the mlag reload-delay ending in 150 seconds, then 30, then it comes back to life five or six minutes after boot.