Rohloff clicking sound with ratchety feeling
I have a Rohloff and have sent some emails to the factory due to severe oil spill (had to replace the seals, successfully). From what they have told me, the 25ml of oil is more than double the necessary amount for the hub to work fine, since the oil is very sticky and it distributes inside the hub. Even the unavoidable oil "sweating" should be considered normal, they say.

Recently, I hosted a rider which had a very heavy bike, with 40.000+ on the bike, going to Patagonia (South America). He ultimately LOCKED the hub, being only able to push the bike, not pedal forward or backwards. Rohloff replaced the hub for free, but he had to travel to the capital 1600km away to receive the package :o(

I doubt very much that lack/excess of oil is the problem. I agree with what folks are saying about the chain/sprocket (either too tight or otherwise defective, with a frozen link, or a bent chainring tooth).

What I suggest you is to isolate the drivetrain from the problem: be sure the chainring, chain, sprocket and chaintensioner (if any) are not generating the click.

If not so, write to Rohloff describing your problem as thoroughly as possible, they are VERY supportive.

The not-so-good news is that Rohloff, besides being a marvel of engineering indeed, is not as nearly as bomb-proof as a lot of fanboys tend to propagate, if it is used hard for a long time, some part replacements are unavoidable.

And even with Rohloff, some defects can appear, and the exact building of the hub has changed over the years to avoid common patterns of failure detected.

Unfortunately, it is not possible to be sure if the hub is defective or not, at least via this site, but I hope this helps. Any question in the comments, and I'll be ready to answer.