equation solving – Problem with NSolve: solutions change depending on the choice of the domain. The results are inconsistent


I need to find numerically the roots of a complicated function of a single variable ‘ωDay’. For that, I use NSolve. Since I have potentially an infinity of solutions, I want to solve within a domain. But when I extend the domain, sometimes I loose some solutions I used to have in a smaller domain!…

For example, if I look for Abs[ωDay] smaller than 1 or 20, I get, in the same order, the following answers:

{-0.68529 + 0. I, -0.343457 + 0. I, 0.167332 - 0.21923 I, 
 0.167332 + 0.21923 I} ; {0.167332 - 0.21923 I, 0.167332 + 0.21923 I}

So in the first instance – Abs[ωDay] smaller than 1 – Mathematica finds two more solutions than with Abs[ωDay] smaller than 20. How is it possible, and how can I trust the results I get then? What could be the problem?
Thanks a lot for your help!