I assembled it with my son in half a day. It takes 3-4 hours or more. He likes it. Here are my concerns: #1 - In step 1 you need to assemble C5, C7, C6 and C8 in the order listed. WHY? I didn't understand it, so later I had to disassemble the puzzle to fix it. Everything else is sequential. This is a bug that Roku needs to fix. #2 โ Part A-7 is the corkscrew where the balls roll. I broke the bottom trying to reattach it. Used Gorilla Glue to fix the part. Smoothed out (didn't need sanding) and then reassembled properly. #3 - After completing the puzzle, the racks (part E10 assembled in steps 7-12) (6 of them) do not lift and do not lift easily due to friction. We didn't realize it right away and when trying to turn the crank the wooden pin (G10) broke off the auxiliary gear (D8) (installed in step 3). I glued D8 to D16 (big gear) which solved the problem. I decided to use a Q-tip to apply WD-40 to the underside of the "E10 part" (the assembled parts are called parts d, e, f, g, h, i - 6 of them) where they slide over the top edge of the wheels (D15) for relief slip. It worked! This is a very creative puzzle and my son loves it. It was more work than it should have been, but that's ok. I left this review to help others avoid these problems.
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