D Flip Flop Toggle -- Q into Hex Inverter into D, Unstable Output, Help
To fill out the comments a little, the problem (I suspect) is that your debouncing RC circuit is incorrectly sized. With \$C=3.3\ \mu \mathrm{F}\$ and \$R = 100\ \mathrm{k}\Omega\$ gives a time constant of \$0.33\ \mathrm{s}\$. Your traces show that when you close the switch, you get a nice clean edge (as you'd expect). When you release the switch, the capcacitor starts to charge. Using the equation \$V_C = V_\mathrm{in}(1-e^{\frac{-t}{RC}})\$, you can rearrange to find \$t = -RC\ln(1-\frac{V_C}{V_\mathrm{in}})\$. Using the values of \$V_{IL} = 1\ V\$ (maximum logic LOW input) and \$V_{IH} = 4\ V\$ (minimum logic HIGH input) from the inverter's datasheet shows that the inverter's input is in an undefined state (\$V_{IL} &lt; V_\mathrm{in} &lt; V_{IH}\$) for about 460 ms. This is consistent with you seeing an extra transition at the midpoint of the trailing edge. Try reducing the value of either \$R\$ or \$C\$ by a factor of 10, and ideally also use a Schmitt trigger input inverter as suggested in the comments.