Using strace on kdenlive, it looks like you close file descriptors from 0 to 1023 from no reason whatsoever. There is no reason to do this. Are you even tracking the open files or you leak them? In any case, on exit it doesn't even matter, the OS takes care of it. See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=869838
Is this still the case with Kdenlive version 18.08.3? I’m not a developer. Can you explain me in more details?
This does not appear to be a bug, but rather a question of software design.