Symmetra LX dropped load after 7 seconds

[BillP]

We had a power outage last Friday at 1:44AM and our Symmetra LX dropped the load after only 7 seconds. The Symmetra is 5 years old and we have replaced all batteries and several power modules (due to failures) over the last year or two. It has 4 power modules and 4 battery modules. It operates at about 30% load and 33 minutes of runtime.

When I came onsite at 3AM, all 4 power modules indicated they were failed and the entire load was still dropped. Putting the unit unto bypass via the front breaker did not power the load. I power cycled the UPS and still had to re-seat all 4 power modules to get them to come online. We have a generator backup that had started, but the APC did not pick up the load until after rebooting and re-seating the power modules.
It seems to be working fine since then, but I now have no confidence in the unit.
The APC tech came onsite and did not know why this happened and offered no definitive resolution. Any thoughts? TIA
Attached is the log:

06/24/2011 01:56:58 UPS: Load shutdown from bypass; input frequency or voltage outside limits.
06/24/2011 01:56:58 UPS: No working Power Modules.
06/24/2011 01:56:58 UPS: Power Module failure.
06/24/2011 01:56:58 UPS: Communications established.
06/24/2011 01:56:39 System: Network service started. System IP is 10.20.50.91 from manually configured settings.
06/24/2011 01:56:39 System: Warmstart.
06/24/2011 01:45:06 UPS: No working Power Modules.
06/24/2011 01:44:53 UPS: Turned off.
06/24/2011 01:44:52 UPS: Power Module failure.
06/24/2011 01:44:46 UPS: Load shutdown from bypass; input frequency or voltage outside limits.
06/24/2011 01:44:39 UPS: Switched to battery backup power.