To test the lens calibration reassemble the console up to the ground springs near the memory card slots.

The memory card ground springs MUST be put back on prior to restarting your console.

If any further adjustments are necessary just turn the potentiometer no more than 1 or 2 degrees more per readjustment. Eventually you'll start to see less DRE messages.

Once there no more DRE messages, turn the potentiometer a further 1 degrees to "future-proof" your lens from DRE messages in the future.

As stated in the title of this guide. This procedure may not fix your DRE problems if the faut lies elsewhere in the system. But this will cover about 98% of DRE messages.