I have a friend that had 3, yes 3 110's start knocking, two were softails, 1 was a Dyna, dealership looked after him, they were not allowed to open the engines to see what was up, mothership wanted them back intact unopened, not saying this is what is happening here but pull the oil filter, cut it open and inspect, if there is any metal....well, it's on them.
I have a 110 softail slim S, from new, no issue with knocking but ever since my mates experience I have a list put together of bits I will need to bullet proof it if it happens to me.

 

What’s on your list Hilly?

My list starts with lighter valve springs which I bought. Still waiting for usps to deliver my fancy new lifters from WFO Larry

 

IF it goes bang a Darkhorse crank and go up from there.

 

Ever get it figured out???

 

Got my Twin Cam back from the dealership after putting on the SE 110" tire shredder kit. Had a very loud, distinct tick that it didn't have before. Rode 100 miles, still ticking, Listened with my bare ear and swore it's coming from the rear lifter galley. Bought one of the cheap mechanics stethoscopes from A'zon that has the long metal rod coupled to a goofy amplifier chamber. Started touching the end of the rod against different locations and, clear as a bell, the tick is coming from the exhaust side of the front rocker box! How did I go 50 some years working on stuff without this tool?

 

I bought one over 50 years ago. Back then it worked real well. Now days, not so much..