It is a known issue that is being tracked in the Dev Tracker section of the forums. I linked it below. If you have specifics to add to the conversation please add them in that thread since it is now the official thread.
We are aware of this issue with the Guild Finder and a fix is being worked on. For the time being we recommend making your search criteria as specific as possible. The issue you're experiencing will happen when search criteria is broad and the corresponding results are extremely high. Since there are multiple threads already about this topic, we are going to close this one.