Are you sure tolerance is not a problem?
Passive components have tolerance ratings. The posted tolerance indicates the maximum percentage from the correct value (divided by 2) that the value can be wrong.
For example, if you have a 5% resistor that is 1K, the actual value can be anything from 2.5% below, to 2.5% above.
In this example, the resistor can be from about 975 ohms to 1.025K
Capacitors also have tolerances, but they are generally worse.
These components affect the frequency on a 555, and their values should be double checked. if you need accuracy.
Maybe something you have is broken.
Perhaps you should choose different RC values, so you can obtain a lower capacitor. Why? because the larger value the capacitor, the longer it takes to start.
If you are using electrolytic, try a different type of capacitor.