Problem with Rendering Candle Flame with RGBA transparency

I have a problem and I can not find an answer in internet. So basically I have a candle with animated candle flame (made with texture nodes and I added a point light source) and I want to render only the flame animation, because other things are static, and then combine the static image with the animated. So I need candle flame to be with a RGBA information. However, when I render it, it gives very weird result. So in the upper part this is how it looks in the viewport, and in bottom part it’s how it looks when rendering.

And it is the same in Cycles or Eevee. Could someone please tell how to fix that, if it is even possible?

So I reply to this by myself. It might be useful to someone. I found an answer in stackexchange. So either use OpenEXR format instead of PNG, or download new Blender 2.91 and then it seemed to be fixed with PNG format as well. But when I saved it in PNG, it was again weird. So, I guess, just need to stick to the OpenEXR then.

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