For what this is worth... I'm running a fully-updated Lubuntu system (18.04.3 LTS) and I'm still seeing this problem with leafpad and smb shares. Leafpad shows version "Leafpad 0.8.18.1" on the help/about screen. It appears that there was a fix released in Debian 6 months ago, but either it didn't make it down to the lubuntu repositories, or it didn't get fixed.
For what this is worth... I'm running a fully-updated Lubuntu system (18.04.3 LTS) and I'm still seeing this problem with leafpad and smb shares. Leafpad shows version "Leafpad 0.8.18.1" on the help/about screen. It appears that there was a fix released in Debian 6 months ago, but either it didn't make it down to the lubuntu repositories, or it didn't get fixed.