It appears these Lutron MIR-600THW dimmers, in spite of their relatively high cost per unit, take the cheap design shortcut of deriving their operating power through the load. LEDs (and CFLs for that matter) flash because their power requirement is lower than the power required by these dimmers in standby mode. What you need is a 'Three Wire' (NOT '3 Way') dimmer. It will have an input wire (black), an output wire (red) and a neutral wire (white). The always live black and white connection will provide power to the dimmer without placing the dimmer in series with the LEDs. This in turn will keep the bulbs from flashing from the current flowing through them. Good luck finding them, you might have to go beyond the consumer level stuff.
Edit: You might also be able to stop the flashing by adding as little as a 25 to 40 watt bulb, instead of a 65 watt PAR30. YMMV
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