It's not really the curbs giving me silly bounces, but instead the random grip and grab I get from the inside curbs in low speed. Maybe it is my imagination, I don't know.
T3 curb gets me good. A couple at Silverstone do it too, one being Becketts. Sometimes I think I'm clipping inside the curb and that's pulling the inside front tire, but then sometimes I'm just barely on the curb and it sucks me in. Not really sure why. The curbs on exit don't really bother me, as normally that is predictable.
I'm not sure if you are comparing it to other simulators or taking reference from real life (I can't do that sadly) but for example in iRacing the curbs upset the car aswell (in Silverstone especially). I think LFS doesn't really have curbs simulated too well, they are just a bit less grippy parts of asphalt, at least that's how I feel about them. AC curbs really feel like they need some improvement though, especially the curbs on Mugello I think. Someone must've made them drunk.
Curbs seem fine to me. The problem is the weird bouncing the car does when it lands. The 458 S3 at Monza, in the second chicane, always gets me. I go over the curb on the right, clip the curb, and the car just continues bouncing and bouncing, all the way out the the exit.