Inconsistent light emitting by lava & colored glass with RTX

When placing colored glass (in my case: light blue) in front of lava, the emission seems to be emitted inconsistently. On one side, the lava glows, emitting a quite warm light, on the other side the lava texture is completely blue, also emitting a blueish light. This happens with different texture packs (Screenshots: Kelly's RTX and Defined PBR). Sometimes, one can see that the texture even flickers between both states.