Rollback of 1cda1e7a8c, fixes #3163

Note this change re-opens issue #2472

PiperOrigin-RevId: 884378131
Change-Id: Ifefc345f1a296e5245cbb10047bb678ffea3598f

src/engine/engine_setconst.c

@@ -737,18 +737,8 @@ static void set0(mjModel* m, mjData* d) {
       }
 
       // average diagonal and assign
-      mjtNum tran = (A[0] + A[7] + A[14])/3;
-      mjtNum rot = (A[21] + A[28] + A[35])/3;
-
-      // if one is zero, use the other to prevent degenerate constraints
-      if (tran < mjMINVAL && rot > mjMINVAL) {
-        tran = rot;  // use rotation as fallback for translation
-      } else if (rot < mjMINVAL && tran > mjMINVAL) {
-        rot = tran;  // use translation as fallback for rotation
-      }
-
-      m->body_invweight0[2*i] = tran;
-      m->body_invweight0[2*i+1] = rot;
+      m->body_invweight0[2*i] = (A[0] + A[7] + A[14])/3;
+      m->body_invweight0[2*i+1] = (A[21] + A[28] + A[35])/3;
     }
   }