This is unfortunately a common issue with UE5 and emissive light. It’s an limitation in the engine.
If the emissive light gets to small and to bright it gets really bad flickering issues. There is a few ways to work around the issue, but in the end you still need to either make your emissive source larger or make the emissive source less bright - after doing that you can add normal light sources together with the emissive to get more light cast around the emissive light source.
After lowering the emissive strength you can set bloom method to convolution in the post process volume and crank it up a bit. That will not make the emissive actually brighter but it will be prercived as brighter due to the convolution bloom effect.
You can also try to crank up the lumen settings in the post process volume, when I set lumen quality between 4-6 I sometimes get rid of some lighting issues, but this is probably not a great fix and It’s at the expense of performance.
Emissive lights can be great, but in most cases you should try to use normal light sources (rect, point, spot, directional and so on) for actually lighting the scene to avoid issues.