**Bug introduced in 11.0 or earlier and fixed in 14.0.0 or earlier** `BesselJ[0,x]` is a smooth quasiperiodic function. NSolve is able to find all roots in the given range `0<x<50`: erg = NSolve[{BesselJ[0, x], 0 < x < 50}, x, Reals] Show[{Plot[BesselJ[0, x], {x, 0, 50}] , Graphics[Point[{x, 0} /. erg]]}] [![enter image description here][1]][1] But if I increase the range `0<x<100` NSolve misses many of the expected 32 roots. erg = NSolve[{BesselJ[0, x], 0 < x < 100}, x, Reals] Show[{Plot[BesselJ[0, x], {x, 0, 100}] ,Graphics[Point[{x, 0} /. erg]]}] [![enter image description here][2]][2] Any idea why NSolve fails? Is there some kind of *critical argumentsize x* in the definition of `BesselJ[0,x]`? Thanks! [1]: https://i.sstatic.net/Yr5O5.jpg [2]: https://i.sstatic.net/ol2co.jpg