try this.
put it on the scales. when balancing dont do anything but diagonal adjustments. if lr and fr are heavy lower the ride height together and also raise the rr and fl together. do this until its balanced.
now go to the ride height gauges. this time do not adjust diagonally. adjust 1 at a time to get the ride height correct.
go back to the scales and do it diagonally again.
you may have to do this series 2 or 3 times for a chassis that looks flat but has never had the ride height and spring compression aligned.
dont read further if this solves your problems.
If your car wasnt flat or has some diagonal preload or one side of the car flexes more than the other this will sequence will make it hard for you to see it in usual ways. it will still jump to one side under acceleration but the chassis will appear flat. you wont get the tale tell signs of tweak. the springs will redistribute the static weight and collar length but under load everything will be off. Be sure the chassis is flat.
be sure the chassis is flat before you do this method. the best way to make sure its flat is on a piece of glass or whatever then to replace shocks with tie rods and make sure the chassis is still flat or level at ride height. if you put a 5mm shim (for example) under the lr tire and the front left (just keep shimming until one of the corners comes off the ground) tire comes off the ground 2 mm move the 5mm shim to the rr and expect the fr wheel to come off the ground 2mm. if it doesnt the car isnt flexing properly or it is preloaded to one side. loosen the top deck and get it to flex even from left to right.