I just replaced all bulbs in my Future Spa and it looks amazing! To fix the flicker issue, I used Comet Pinball's Ultimate Optix LEDs. These LEDs are "engineered for Superior Non Ghosting, Non Flickering, and reduced Strobing."
Unfortunately, there are still 2 LEDs flickering. One LED that flickers I can live with (the Special insert which rarely comes on), but the other LED is right in the middle of the playfield and in a line of LEDs of the same color. So it does standout badly.
Any ideas what I could do to fix this one LED? Obviously, the Optix LED has a resistor built in so does it need more resistance?