Uneven illumination of LED lights may be caused by a variety of reasons, here are some solutions:

Check the power supply: Make sure the power supply voltage is stable and meets the rated voltage of the LED strip. Voltage fluctuations may cause some LED beads to be unevenly lit.

Troubleshooting shorts or breaks: Check the strip for physical damage such as shorts or breaks, which may cause some of the LED beads to not light up or have different brightness.

Adjust connections: Ensure that the power connections to the LED strips are correct, especially when splicing multiple sections of the strip, make sure that the positive and negative terminals of each section are correctly aligned.

Replacing bad LED beads: If you find that individual LED beads do not light up, try replacing them. This usually requires some electronic knowledge and tools such as a soldering iron and new LED beads.

Parallel design: If the strip is designed in series, the failure of some LEDs may cause the entire strip to lose brightness. Consider using a parallel design so that if some LEDs fail, others will still work.

Use a controller: Some LED strips support PWM (Pulse Width Modulation) control, which allows the controller to adjust the brightness to reduce unevenness. In addition, some advanced controllers have colour balancing features that help improve brightness consistency.

Replacement: If none of the above methods solve the problem, you may need to replace the LED strips with a new one. Choose a better quality product when purchasing to reduce the likelihood of uneven illumination.

Please note that it is important to disconnect the power supply when dealing with LED strips to avoid the risk of electric shock. If you are unsure how to proceed, it is recommended to seek professional assistance.