2002 VW Passat 2.8L Fuel Trim Bank 1 Too Lean (P2096) After O2 Sensor Replacement

I've been experiencing an intermittent P2096 fault code — 'Fuel trim Bank 1 too lean' — occurring roughly once per week. The issue typically appears about 10 minutes after starting the engine, at speeds below 30 MPH and with low RPMs (between 1350 and 1550). There is no noticeable loss of power when the check engine light activates. This problem began approximately one week after I replaced the Bank 1 O2 sensor with Bosch #16073 sensors. Although my catalytic converters are 14 years old, no other trouble codes have been triggered. Given the infrequent occurrence and lack of symptoms like power loss or rough idling, I suspect it's not due to a vacuum or exhaust leak. I consistently purchase gasoline from Costco, so fuel quality is unlikely to be the issue. With no additional diagnostic errors, I'm at a loss as to what might be causing this. I'm concerned about potential long-term effects and am considering taking the vehicle to a dealer — which would be costly. Any insights or troubleshooting steps would be greatly appreciated.