If you are having issues inserting wires into your push-in wire splice terminals, you may want to strip the wire shorter, also make sure you are inserting the wire directly in the center of the terminal.
In the HelaCon Plus Mini series you will notice a small wire indentation channel directly in the center of each contact. Making sure the wire is cut to just enough length and placed in this channel before pushing in will ensure the wire will not bend. Having multiple positions of these laying around are handy whether you are using them on 22awg breadboard wire or on 14awg house wire. These are flexible enough to fit 22awg down to 12awg, no more need to look around for that right size wire nut once you have these in your toolbox.