Yep, having the exact same problem with my Rival levers. Oddly, I only seem to notice it on my homeward commute, when it's felt fine in the morning. I haven't bothered threadlocking it because my hamfistedness means I'll probably drop the screw while trying to take it out. I'm just tightening it up again whenever I notice it, and it's fine until the next time it does it again
Yep, having the exact same problem with my Rival levers. Oddly, I only seem to notice it on my homeward commute, when it's felt fine in the morning. I haven't bothered threadlocking it because my hamfistedness means I'll probably drop the screw while trying to take it out. I'm just tightening it up again whenever I notice it, and it's fine until the next time it does it again