Hi Dionysios, sorry for the delay, and thank you for an amazing video recording! If only all user reports where that clear!! :)
I have managed to successfully reproduce this with the newest daily and 3ds Max 2019, BUT the material is actually saved into the library - the list is just not refreshed. So if you stop IR and put one more material into the library, it will get refreshed, and you will actually see 2 new materials. So the saving is done, just the list is not updated. We will look into it anyway, but I guess this is a 3ds Max limitation, where it cannot render the thumbnails while actual rendering is running.
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