As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
STL - FLT 3400 - IN CRUISE FLIGHT, FUEL QTY STARTED TO INCREASE IN THE CENTER TANK, WHILE LEFT WING TANK STARTED TO DECREASE. CREATING A 600 LB IMBALANCE IN THE WING TANKS. REMOVED AND INSTALLED TUBE ASSEMBLY IN LEFT CENTER FUEL TANK. OPS CHECK GOOD IAW CRJ 700 AMM 28-21-15. (M)