The problem if the FireWire ports was reported several times when the RM mixers were new. It seems that PreSonus has improved the manufacturing, this problem is no problem any longer. You may also consider a repair. Ask your distributor (not your shop). A repair is probably much cheaper than buying a new option card. You will be asked to send the rack mixer for repair, not just the option card.

Generally there is no question about the "built quality" of PreSonus products. Of course there can be problems here and there, especially when a product is new, but I would not have bought so much PreSonus stuff over the years, if the quality was bad or not good enough. I not a PreSonus fan-boy. The stuff works for me, that's all.