Tab issue for somewhat newbie

Cutting out this board. Two separate cuts, but setup basically in the same place of the wasteboard with the same exact board. When I cut out the one on the left, I lose the middle piece (tried twice), but when I cutout the second one, my tabs hold and it doesn’t break apart? Do I need to make the tabs bigger? Using default tab size (length .25 and height .08). Am cutting on shape for both

Could be several issues most likely the board isn’t truly or consistent in the same thickness over its entirety. Is the board perfectly flat? if it has a slight bow to it this will also cause it not to cut consistently as it will have high and low spots for the warped board…

This might be of interest, no tabs by using masking tape and super glue:

Your main problem is that your wood is weak, compounded by the factors Steve mention.