That could be just due to going with 2 liters over the 1.67 liters factory fill. When I went to 2 liters with the oem stuff, it got rid of that clack noise as well.
OK, fair enough on that point, but still just cannot recommend the Ford DCT fluid in a non-DCT gearbox. I can only recommend a full synthetic *gear oil* that meets the exact Ford spec and I've found that only Ravenol MTF-2 and MTF-3 does this. And as far as other full synthetic GL-4 gear oil out there, why stray at all from one that actually meets spec too with such a picky gearbox?
Although I highly doubt it was the Motul's fault in OP's failure, it is a fact Motul does NOT meet the Ford spec for our car. Unlike with even EXCELLENT motor oils that doesn't all meet exact Ford spec, our gearbox is very picky so why risk it? Also, even though there are a number of DCT fluids that do meet spec, I see no reason to use it at all in a gear box when there is actual gear oil available. Especially after seeing what nasty, grey and watery crap OEM fluid drained from my trans, I refuse to believe that provides proper protection for a gearbox. I truly wonder if Ford realized they had so much DCT fluid produced that they decided to use it for cost cutting purposes. Especially since the FiST came out a couple of years after the half baked DCT in the base cars it makes you wonder. Whether someone feels that is wild speculation or not, I dare anyone who hasn't seen the OEM fluid drained to try it and then honestly tell me that they think that would properly protect an actual gearbox. While the Ford DCT's are a "dry" clutch model, they still have their own characteristics to meet with fluid that does not apply to a manual gearbox.
The bottom-line is that Ravenol MTF-2 (75w80) and MTF-3 (straight 75w) are the only full synthetic gear oils that do meet Ford spec. If you use anything else at all then you can't be surprised if you have poor performance or failures. Nothing personal to anyone, truly, so if you are using something else and it works great for you, that's fine. But with such a picky gearbox I can't see anyone justifying recommending anything else at all that doesn't check off all the boxes: right type of fluid (gear oil), full-synthetic, and meets spec, which is WSS-M2C200-D2 for your searching pleasure. I am not a fanboi or stock holder of Ravenol, it's just in this case this is 100% clear cut what we should use and recommend to others.