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]]}]

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]]}]

Any idea why NSolve fails? Is there some kind of critical argumentsize x in the definition of BesselJ[0,x]? Thanks!