This is a common problem on dual cabinet
systems. They do need to be Synchronized
at start up.
A good UPS with true voltage correction is the way to go. Trippp-Lite, APC and ONEAC all make decent units. You do need true voltage
correction not just battery back-up
give me your fax number and I'll send you the Snyc. procedure if you need it.
If you have poor AC power your going to have problems no matter what brand or type of system your running.
Hope this helps.
WAM