Touchscreen doesn't work!

[github4mat]

I have the same problem with the touch screen calibration as "sbfreddie" reproted years ago. The problem I found is, that first time after touching the screen the tft.touched() delivers true value for return but touching again it stays false! The reason may be that _RA8875_INTS aren't not being cleared and so the statement "if (bitRead(_RA8875_INTS,0))" wont deliver true after first time passed!
Doesn't this statement "_RA8875_INTS &= ~(1<<0); _checkInterrupt(2);" clear the variables correctly?
I dont know how to check this?

My hardware:
Teensy 3.2
5' Adafruit 800X480 TFT Screen

#define USE_RA8875_TOUCH //resistive touch screen is being set!
Interrupt pin is pin 0;
Version of RA8875: 0.70b11p10
Can someone help me?