Like you, we have a 2018 trailer, a Raptor 353TS. About a month ago, we had much the same experience. After about 3 years, the shackles and other running gear were junk
We hired Performance Trailer Brake to replace the two 7K axles with 8K axles, 8K leaf springs & hardware, three MORryde cross members, MORryde CRE3000 equalizers, MORryde HD shackles and wet bolts, disk brakes, and hubs with 9/16" bolts.
Expensive? VERY! Worth it? Yes, every penny! Our Raptor tows so much better, smoother, quieter, more stable (some of which might be wishful thinking, but not all for sure). I can tell you that the whole rig will stop straight - and faster with the trailer - so much so that I have had to rethink my tie-down plan for the SxS in our garage. I really don't want it to end up in the main cabin on the couch after a panic stop!