1 screw each end, top & bottom and on both sides is not enough to keep the gate square. Your gate has clearly dropped and is out of square. Also the small 'u' channel which the ends of the infill sheet slides into is twisted. There is a very simple solution to having and maintaining square gates which are fabricated on site. 2 screws minimum both ends, top & bottom and both sides plus 2 screws each end under the bottom rail and on top of the top rail. Also, I place 7 small colour-coded rivets down each side of the front of the gate, through the small end u channel to prevent the infill sheet from moving within the gate frame. This locks everything in and it can't move, drop or twist. This method also works perfectly when you have a custom sized gate which requires more than 1 infill sheet. In this case you add 7 rivets down the overlapping joint of the 2 infill sheets as well as down each end through the small u channel. Colour-coded rivets will ensure they blend in with the rest of the gate and 'disappear'. It is neat and tidy and so much stronger and sturdier than just using 8 Tek head screws in total. 😁