Decreased CO2, Increased DO in Brite Tank after Kegging

[Gilgamesh1]

We recently started seeing decreased CO2 and increased DO in the brite after kegging half of the tank. Any ideas why this might be happening? Here's our process:

1) Purge brite, confirm successful purge with Anton Paar cBox
2) xfer beer to brite, carb to desired CO2 and check DO reading (i.e. 2.4 CO2, 25 ppb O2)
3) keg 50% of batch while maintaining head pressure with CO2
4) measure CO2 and DO after kegging... and CO2 drops to 2.2 and O2 increases to 75 ppb

This is just an example but it's something we've seen 3 times in a row. Any ideas?

[vinaykumar27]

To answer your question, I have a few follow-up questions:
1. Do you purge your kegs as well?
2. Do you have a check valve between your brite and keg-filler?
3. Are you checking CO2 and DO in your kegs or brite tank?