Anyone had problems with a recone job?

I've got an old JBL B380 sub. Not my preferred sub, but what can I say, it was cheap.

The 2235 15" driver had foam rot. I took it to the local JBL dealer to have it reconed. After the recone, it just doesn't seem to handle the power like it use to. Seems to bottom-out quite easily.

Does this mean it wasn't hung properly or are there other mistakes that could have been made?

I'm driving it with a 500 watt Sunfire sub-amp.

Any thoughts would be appreciated.