Hi,
Sorry for the issues you are having. It sounds like your venues do not have coordinates and so they are showing as 0,0 and that is off the coast of Africa.
We have a way to edit the venue coordinates in the next release. In the mean time you can use the Event Rocket.
It is an unofficial plugin maintained by some of our developers:
Event Rocket
Once added you can see the coordinates in the venues and manually add them.
As for why some may not work and other times they do. Our coding sends the venue’s address and in return we get coordinates. If there is an error or no connection it defaults to 0,0.
If you are on a shared hosting it is possible another site has used the daily traffic to contact the google map api and that is why some addresses do not get coordinates too.
Does that make sense?