Door contact tamper issue

[Newbie-texe]

Installed a grade 3 surface CQR door contact on a clients Aluminium sliding front shop door. 
contact works fine open/close everything is fine. 
however it randomly causes a tamper alarm and then goes back to normal.  Not always at the same time. Some days no tamper. What seems to be causing the issue. Never had this. Changed the sensor to a new one. Checked all the wiring and gaps ect. Still the same issue

[james.wilson]

Assuming it might be external interferne have you tried excluding that with a masking value? 

Whats the risk I'm assuming high if grade 3 contact 

[sixwheeledbeast]

To expand on above.

Most likely the interference reed is picking up the magnet because of how it's mounted.

Not every door frame lends itself to having hassle free G3...

Does the site need Grade 3? If not don't use it.

If a Grade 3 system have the interference reed trigger a fault not tamper to rule out an intermittent tamper issue.

Probably just millimetres off being in the sweet spot, if the instructions have been followed exactly.