This issue is related to maximun number of light that we can handle inside a Tile. This limit have been increased to 64 recently.
To see it, you can open the rendering debugger and select the Tile/cluser debug mode and switch to a verison of it, it will display number of accepted light per tiles and show you reached the maximun. There is nothing we can do above this maximun - this is the limit of your system, you need to reduce the coverage of your light to avoid to have so many overlapping light.