Those ceramic saddles are notorious for imbalanced sound, even though the saddle has slots to separate the four parts, it's still only one piece. The tray the saddle sits in has four individual pickups, so sometimes the saddle does not put even pressure on the them. The remedy I found here on TB years ago is to remove the saddle, cut all the way through the slots to make four separate pieces (i used a thin Xacto saw blade), carefully replace the pieces in the tray, you might use a little tape temporarily to do so. I've done this to four or five of my bass ukes that worked perfectly.
View attachment 4729860