I have three separate Curado reels that all make a similar grinding noise on retrieve only. It sounds like something isn’t catching and is slipping. I’m thinking it might be the anti reverse bearing? I fish strictly saltwater as well. This has been driving me crazy trying to find the problem. One reel is only a few months old and I have oiled the bearing around the pinion gear which maybe be too much. Also all three reels look like the attached pic. Any help is greatly appreciated.

Those bearings are trashed if they all look like that…I’d venture to guess that the bearing on the reel handle is wrecked too…they need a good cleaning and then replaced with some upgraded bearings

lets not forget those handle bearings are also trash!

When fishing salt water the reels need to be rinsed after every outing.

tmd11111 said "When fishing salt water the reels need to be rinsed after every outing".

Not just outside. You need to open the side cover, remove the spool. Get ANY salt water out. When salt water evaporates, the salt crystals remain and they grow, They will jam up bearings, bushings and fill any crevasses, so that things that are supposed to move will seize up. I almost killed a Chronarch, letting it sit for weeks after a wet salt trip. The hammer I had to use to get the side cover off broke it!
Now, after every trip, I pop out the spools, dry everything, and oil the bearings, the level wind parts, the handle bearings, and when I grab a reel, it's ready to fish. Even doing that, my Shimano sounds like a 12 volt winch! I'm using Piscifun baitcasters and they're quiet. Every couple of months, I disassemble the gear side and clean and lube everything. The Piscifun's have about half the internal parts versus the Shimano, but work better for me. I have finally learned how to not re-assemble my reels wrong! My advice is worth what you paid for it. Good luck. IslandJim