Check the Blow Back Valve Blocker, if they copies the TM's to a T and are using cheaper plastics, this use to be a problem on some of the earlier P226 versions when they first came out. You will need to take your slide off, pop out the barrel and hopup unit, then the nozzle inside the nozzle theres a little itsy bitsy screw which holds the valve blocker in becareful when removing it as it is holding in you valve and a small spring so dont loose it. Check for hairline cracks in the blocker. It cause all sorts of issues on mine when I first got it, till I swapped it out for a Guarder enhanced one. Larges issue was not recocking and wasting gas.
Here a break down repair manual of the TM's so you can identify parts:
http://tech.airsoftcanada.com/TM/TM%20-%20P226/
The valve blocker is on page 1 - P226-17