Neptune, Apex, trident flickering light when testing

[juboy27]

I have a trident tester and when testing the light and the light inside the test vile flickers any ideas anyone thanks

 

[vetteguy53081]

I have a trident tester and when testing the light and the light inside the test vile flickers any ideas anyone thanks

Is the vial clean. Sounds like the photometer is trying to read but having a hard time reading the sample