Fun little game jam game! I noticed that the target lock seems to go after the first enemy on the screen even if the turret is aimed at a different enemy. I gave the game a few tries, but this made the strategy element feel off as it didn't matter where I placed turrets at higher levels.
Overall great game!
You are right about this bug, and sadly I first found it after the jam ended. I have fixed it, and few other small bugs. If you are interested I have upload a new version, on my Game Jolt page, and you can find it here https://gamejolt.com/games/1981/843055 . The game is mostly the same, but I have fixed some of the games bugs.