Look at the sphere where the light probe is placed. In deferred it shows noise, in forward it does not. This could be an issue with forward rendering, considering the probe contains these noisy areas. Needs more investigation.
Probably a light probe gen issue, due to the insane sampling done to generate these it has to be a math bug somewhere in the code. Haven't seen it in my scenes but I need to re-visit a good GI solution at some point.
Check out the "lightprobe-bug" branch.
Look at the sphere where the light probe is placed. In deferred it shows noise, in forward it does not. This could be an issue with forward rendering, considering the probe contains these noisy areas. Needs more investigation.