I don't know if anyone else is having this problem, but on the map where the bloons are on a wall, towers I place near the top wall only shoot relatively directly in front of themselves. They won't turn and shoot, even if bloons are in their range, until I buy a monkey village to increase their sight.
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 "Bloons TD 5"){kind=icon}
 "Toss the Turtle"){kind=icon}
 "Sonny 2"){kind=icon}