Two PWM output interfering with each other.

Hello everyone, I am using arduino uno to receive measurements from two HC-SR04(ultrasonic sensor) and generate PWM output accordingly. But if there is any obstacle in front of say Sensor1 , but Sensor2 is clear, output1 along with output2 is responding(the response of output2 is comparatively very small tough). But Vice Versa not happening (i.e. When there is a obstacle in front of sensor2 but sensor1 is clear everything is working fine).

i have tried 1. changing the sensors 2. using a external BC547 made swithing for load enhancement 3. adding timeout to Ping function

Please post your code between [ code ] tags.

Is it possible that sensor 2 is able to see the echo from sensor 1? It may be bouncing off the back wall and arriving at sensor 2 part-way through sensor 2's measurement cycle.