JM -- I know of accidents of three types that involved rod-end failure.
First was one in which the rod-end bearing was not locked in place by a jam nut, tightened against the threaded insert in the push rod tube. The bearing was able to move up and down slightly in the threaded insert, eventually causing the threads in the insert to strip. The rod end bearing then was no longer attached to the pushrod tube.
Second, the threaded stem broke off the bearing housing (ring). This can be caused by bending loads on the stem. This, in turn, can result from the use of a control fork (upper or lower) that restricts the bearing's tilting action as the controls are moved to their limits.
Third, I have heard of (but never encountered myself) bad welds in the round housing in the 2-piece bearings. The round housing, or ring, breaks in half (for instance, it may break at the 3 o'clock and 9 o'clock positions) releasing the ball.
I have not heard pf a pushrod tube itself breaking. These rods are critical in compression (column loading). Resistance to column loading is more a function of the DIAMETER of the tube than the material it is made of. Example, the Gyrobee plans call for pushrod tubes of 9/16" diameter x .065 wall 4130 steel. Despite the use of steel, these rods are weaker in compression than, say, an Air Command pushrod of 7/8" diameter and .058 wall 6061-T6. Neither rod will withstand more than about 200 lb. of compression without buckling -- the 9/16" steel a little less than 200.