My DFRobot sensor output fluctuates wildly under stable supply

Hello everyone . I am fnf— I’m working with a Gravity analog pH sensor (SKU gravity‑pH) and feeding it a clean 5V supply. But when I leave the setup idle, the pH readings swing ±0.5 unit over minutes, even though the solution and temperature are stable. I’ve double-checked wiring, replaced the ADC board, and added decoupling caps — still no luck.

Has anyone seen this random drift behavior? What steps or diagnostic tricks would you try next?