Mixed Exhaust Vents
For Proper Ventilation, both high and low vents should be installed. On paper, the high vents are supposed to act like exhaust vents while the low vents should act like intake vents. Convection is supposed to help make this happen. In reality, it all depends on how the wind blows, convection has little to no effect, and it's never perfect. The intake vents will typically be soffit vents, while the exhaust vents may consist of ridge vents, turbine vents, box vents, or powered vents... But only one of those.
When Different types of rood vents are installed, there is an increased potential for air in the attic to basically short-circuit. The solution here is to install only one type of exhaust vent.
Crooked Turbine Vents
Turbine vents need to be installed perfectly level; when they're not installed level, they don't turn. The other thing about turbine vents is that they really do pull air out of the attic; if air sealing hasn't been performed in the attic, they'll pull air into the attic from inside the house, and shouldn't be used. That bears repeating: do not install turbine vents if the attic has not been professionally air-sealed!
Insufficient Intake Vents
Current standards specify a 50/50 split between high vents and low vents, but how are low vents supposed to be installed in a house with no soffits? Without any low vents, the high vents will tend to pull conditioned house air into the attic through attic air leaks. One solution would be to install fascia vents, and another less desirable option would be to install a bunch of box vents low down on the roof.