Splotches on Lights Reflections

Hi, I have an issue related to UE-19818 and UE-42488:


I am using ForwardRendering now but I am having this problem since 4.10 a year ago. The “fix” was since then to make the lights non-visible so I don´t see them on the reflections after baking the lightmaps. On the scene I have static spotlights with the default minRougness=0.08 and sourceRadius=~3. Depending on this values the annoying splotches appear or disappear on the reflections:

minRoughness=0 to 0.999 —> SPLOTCHES

minRoughness=1 —> NO SPLOTCHES

sourceRadius<~3 —> NO SPLOTCHES

sourceRadius>~3 —> SPLOTCHES

As it says UE-42488 even if I change the minRougness there are not visible changes on the scene so this parameter is not working since I activated ForwardRendering. But is interesting that when this parameter is on its maximum value (1) the splotches dissapear.
What I found about the sourceRadius is that when the value is around 2 or 3 this splotches appear and they slowly get blurred when the value is more than 10 or 15.

Same issue on my side running 4.15. Source radius of 3 to 10 approximately, causes these ugly splotches.