I also have an 07 Scion TC and we have replaced the master, slave, clutch, all the way around. Everything is brand new and I have the exact problem to this day. Whenever it feels like it I will push the clutch in and go to shift (and gear doesn’t matter whether it’s 1st to 2nd or 3rd to 4th n so on) and it’s like it won’t go into gear. So I will then have to release the clutch and put my foot under the pedal n pull it out manually then proceed to push clutch back in and then into whatever gear I was originally putting it in. And it does this randomly. My mechanic has put in different sized springs just to see what happens and nothing changes except for there had to of been ones to long because the spring would pop off every once in awhile. So that wasn’t the problem. And now that I’m thinking about it I’m pretty sure the master was replaced twice this last time because we thought that was the problem n we just ended up with a bad part the first go round. But no, also not the case because it would be fixed by now. It’s driving me crazy because I’m ruining the tops of every boot n tennis shoe I own pulling the dang clutch pedal back..any info is better than what I have now…thank you