I had the same problem with the rear shock top plates. The ones it was built with were aluminum and broke. The replacements were steel. They where cheap like $2.50 each or something close, but they should give them to you if they know its been a problem.. Just my 2 cents.
Yep, those plates are junk! I replaced mine with some home made plates when I switched to the Highlifter springs. They are not very pretty, but you can't see them anyway unless you look real hard.