What is your scene unit scale? You can probably eliminate the light leaks by changing the LC sample size. But since I don’t know the scale I can’t advise if you should increase it or decrease it.
I’ve tried both of these suggestions (yours and the below) and they never solve the issue for me, changing the LC sample size is the only fix I’ve found.
Is the error due to the irradiance map, or the light cache? You can check if you re-render that region with the same light cache (saved to a file), but with brute force GI for primary bounce. It will help to determine where to look.
I got rid of the light leak. and I have almost gotten rid of the spots. Retrace and turned off world scale and turned the size back down to .020. I have my interpose up to that helped a lot,