Sup guys, I had this same problem this evening. Not sure how long it has been there, only heard that awful sound for the first time tonight - sounded like my miter saw. Exact same sound as Sauron, I mean Nazgul above in his video.
Anyway, took off the cover around the tilt motor - three screws, easy, just take care not to strip them. Everything looked ok. I powered up the solo with go pro in gimbal and tested the full range of the gimbal tilt without the cover on - no sound. So there was the culprit. Cleaned it up, took great care to put it back together without pinching any ribbon cables. All is well.
Of note, I took the tilt motor cover see once before and installed a weight in there as I am using ND Filters. So perhaps something got hung up on my weight (thought I put it out of the way), or I pinched something putting it back together. That was a while back, only thing I can think of.
Peace!