2Pcs 12/24V to 5V 5A 25W DC-DC Step Down Converter, Power Supply Adapter Compatible with Solar Panel, Waterproof Voltage Regulator Car Charging Transformation

It is likely that the over - current protection has been triggered. The reasons are as follows:

1. Load Characteristics: If the load is inductive (such as a small motor with coils), its starting current is large. This easily exceeds the normal current - carrying capacity of the product, triggering over - current protection and resulting in voltage drop.
2. Connection Cable Problem: When the connection cable has poor contact, the resistance increases, the current becomes unstable and excessive, triggering over - current protection and causing voltage drop.

The following suggestions are provided:

1. Check the Load: Connect the load directly with a 5V power supply. Observe whether the output current exceeds the product's specifications and whether the starting - instant current is much higher than 5A to determine if there is a problem with the load.
2. Replace the Load for Testing: Replace the load for testing and monitor the voltage and current of the load. An electronic load is a good choice as it can accurately simulate different loads to help troubleshoot the problem.
3. Use a Larger - Gauge Cable: Use a connection cable with a larger gauge, which can carry a larger current and avoid abnormal current transmission and voltage drop caused by insufficient cable specifications.

Even if the power supply settings are normal, problems with the load and connection cable can still trigger over - current protection and lead to voltage drop. Please troubleshoot and handle according to the above - mentioned suggestions.