ESP32 Custom PCB Occasionally Failing During Production Testing

Hello everyone,

I'm developing an ESP32-based monitoring and control board that is moving from prototype quantities into a small production run.

The prototype boards have been working well, but during assembly and testing I'm seeing a few boards that occasionally fail to boot or show unstable behavior until they are power-cycled. The issue is not consistent, which makes troubleshooting difficult.

Current design includes:

• ESP32-WROOM module
• Multiple I2C sensors
• RS-485 communication
• External power input
• Custom 4-layer PCB

A few questions for those with experience taking ESP32 designs into production:

1. What are the most common PCB-related issues that only appear during production rather than prototyping?
2. Have you encountered grounding or power integrity problems that caused intermittent ESP32 startup failures?
3. Are there specific test points or diagnostics you recommend adding before the next revision?
4. How much margin do you typically leave around power supply and RF sections?

PCB Manufacturing Question:

The next revision will likely be manufactured through PCBWay, and I'm also reviewing panelization options.

• Are there panelization practices that help reduce handling or assembly issues?
• Have you seen breakaway tabs or V-scoring create reliability problems near sensitive circuitry?
• How much board-edge clearance do you typically leave around antennas and connectors?

Connector and Wiring Harness Question:

The final product will connect to external sensors and power sources through wiring harnesses.

• What connector families have proven most reliable for ESP32-based products?
• Do you prefer separate connectors for power and signals, or combined harnesses?
• Have connector-related failures become a significant issue in field deployments?
• Any recommendations regarding strain relief or harness routing?

I'd appreciate hearing from anyone who has taken ESP32 products from prototype boards into small-scale production.