The only time that I have had an issue getting 'stealers is when the even card doesn't have the places on the "board", For example, having the door card out, but not having any event cards that come up in order to put a 'stealer on that card. I have had times in which there has been a lull in the game because no place cards on the left and right tell me to put 'stealers on them. This is the only issue that I have had with the game.
Are you sure you are spawning properly?
1) You travel if either blip pile is empty at the end of a phase, so until location 4 there should always be blip cards remaining on each side.
2) On the event card, each spawn icon refers to both sides of the formation, not one for the left and one for the right. So if the first icon is red with a yellow arrow, then you put a major spawn on each red terrain, regardless of what side of the formation that terrain is on.
The expansion locations sometimes have only 2 colors of terrain, so if the event card only has the other 2 colors there will be no spawn. But in the base game every location will always have at least three colors, so you will have at least one spawn every event phase (until one blip pile is empty at location 4).