"Right Flipper is slow to respond or intermittently responds – I encountered this issue as well. In my case, I swapped the button for the right-nudge with the right-flipper until a replacement can be located. Remove the 3 side bars using a philips head screwdriver, slide the top control panel to the side, unscrew the nuts to the button. Press in on the middle clips and gently slide each connector out. Swap/replace the buttons, re-attach the nuts, re-connect button wires, re-install the control panel and side bars. (*Note: If you encounter a good replacement button set, please let me know)"

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https://www.amazon.com/gp/product/B01MS1GZ5J/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

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I had this issue with the right flipper, and I had some of these laying around from a prior project. I had to take a pocket knife to resize the holes slightly, but I've not had any issues.