As a big Spyderco fan, I carried an Endura as my main edc for several years. Later a Stretch for shorter period of time. Two of my three Enduras and the Stretch, with backlocks and frn out of Japan developed back and forth lock rock. Two I sent back to Spyderco for repair. Both returned unchanged, with significant lock rock. It doesn't hurt the cutting functionality of the knives but I still don t like it.
I have a Delica with m390 steel and one with zdp steel, which feel good in hand but I ve never carried them. I wonder if they would hold up better than my Enduras and Stretch.
I m currently not buying any more Spyderco Japanese frn backlocks .