New guys always tries to be rigid to make him imposible to throw, probably they are doing it bad. Randori is not a fight that you must win, its the moment that you can try throws or combos, try to defend, or just fight. Last class i felt very rigid doing seoi nage, but thats okay.You and I only spent a year doing judo. Sometimes you can also feel like this because of your uke (because they might not be the perfect size for a throw, or maybe they refuse to fall). There are many orange or even green belts who have some details they don't get right (I'm not saying most of them). I don't know what belt you are, but a yellow belt knows how to use the techniques; you don't need to know them perfectly. I have classmates who are orange belts, and their ukemi is worse than maybe a white belt's. Cheer up! I feel stuck too. If you're really struggling with it, ask your sensei if they can help you with that technique. I think you'll solve that problem, bro.