I have the same problem and frustration with all multitools. Besides not locking, that is another reason I never depend on a multitool alone and always EDC another blade. It ticks me how cheapo the blade is made on the Micra with a one-sided edge or whatever the terminology. Maybe Leatherman putting S30V on their new Charges will be the solution. I have had no luck keeping a satisfactory edge on the blade my Gerber "palm-pincher" multi-tool has either.

The only way I can think of, right-off-the-bat, to cope before you get something new is just to review how you are sharpening the blade. Does your method leave the optimum angle for the edge not to wear away too quickly? Just make sure the angle is not too steep. Hope this helps.
Me, a vegetarian? My set of teeth came with canines.