OK, maybe a beginner question. I have noticed this too often on house plants and I believe mostly with Philodrendrons. The new leaf has trouble lifting itself from the stem and/or uncurling. Sometimes they just never make it to full size. Ugly. What causes this? Normal behaviour, lack of a mineral, bacteria, light issues, water issues??
I'm not sure exactly what you are referring to - if you are intending to say that the leaf is not emerging completely from the petiole sheath and either has to have human manual help, or becomes bent the more it tries to emerge, then I understand the phenomenon. If it is something else, I need to see a pic. Usually problems in the emergence of a rolled aroid leaf from the petiole sheath is related to low humidity conditions, as it is moisture that helps to lubricate the inside of the petiole sheath. I've had to help many leaves come out due to incomplete or imperfect emergence due to this very situation.