[Unity2021.2.6] 2D Shadow RenderBuffer Clear Problems

Not native speaker. Hope my expression would be clear. I just found a problem in 2D shadow rendering in Unity 2021.2.6. Here's a recording video.

There are 2 light2D in this scene. They share the same sorting layer. The center one's light order is 1 and the upper-right one's order is 0. At start I just left the center light on and nothing wrong. When I enabled the upper-right light, something wrong happened. It seemed like the buffer rendering shadow can't be cleared correctly. If I drag the upper-right light closely to let the ShadowCaster2D's boundshpere meet lit condition, this bug vanished. Perhaps this bug only happens when there is a Light2D outside of the ShadowCaster2D's boundshpere. (Shadow is short because I modified the original code and reset the shadow radius.)

I tried to fix this and it works. Additionally calling ClearRenderTarget in ReleaseShadowRenderTexture function in ShadowRendering.cs.

Code (CSharp):

1.         public static void ReleaseShadowRenderTexture(CommandBuffer cmdBuffer, int shadowIndex)
2.         {
3.             var colorChannel = shadowIndex % 4;
4.             var textureIndex = shadowIndex / 4;
5.  
6.             if (colorChannel == 0)
7.             {
8.                 //Custom modification
9.                 cmdBuffer.SetRenderTarget(m_RenderTargets[shadowIndex].id);
10.                 cmdBuffer.ClearRenderTarget(true, true, Color.clear);
11.                 //Original Code
12.                 cmdBuffer.ReleaseTemporaryRT(m_RenderTargets[textureIndex].id);
13.             }
14.         }

Simple fix. I'm actually quite greenhand to unity. Don't know if this is efficient enough. Hope unity official will fix this.