When i try the glitch i just get soft locked on the unlocked units screen and can't progress. Am i doing it wrong?

If you are refering to the Any% glitch, then you might do it wrong. To perform this glitch, beat the first level, wait about 3 seconds, open and close the upgrade menu, and then quickly hit the continue button EXACTLY 8 TIMES right after it appears, then wait. In a few seconds the victory screen should appear. If you click less than 8 times, the game'll freeze, and when you refresh you'll be on another level. If you click more than 8 times, the game will glitch out. If you don't click fast enough, the game'll freeze, and when you refresh you'll be on level 9. TheAlphaMudkip was the one who discovered this glitch. Here's a video he made explaining it:

Thanks for letting me know. I also found this other weird glitch that seems to be RNG dependent were you can have your guys walk past the Germans on the last wave. It seems to be triggered by immediately making a second infantry unit.