TLC5940: Dimmer LED only on the Output channel 15

The application has 2 LED drivers cascaded.  Only the second LED Driver and Output channel 15 exhibits a dimming behavior.  VPRG, XLAT, SIN, and SCLK were all monitored using a logic analyzer on the LED driver in question.  All signals were acceptable and matched the data sheet example for setting Dot Correction.  However, the dimming behavior was not exhibited when the logic analyzer was connected to the LED driver signals listed above.  It was narrowed down to the XLAT signal.  If the XLAT signal was measured and grounded via logic analyzer then the dimmer LED was not exhibited.  The issue re-appeared after the logic analyzer was disconnected to the XLAT signal.  This only has occurred on 1 unit.  Any advice is appreciated.