Random upload failure due to bug already fixed upstream

Starting from a "recent" update (recent in Ubuntu, ages-old upstream), I've started getting random upload failures: I upload a bunch of files, and randomly, a few of them fail.

By digging into it, looking at the logs etc, it's clear that there are issues in the sequences of CWD and MKD commands executed by parallel processes uploading files in parallel into the same directory (when the directory doesn't exist at the beginning).

I was looking to report this upstream when I realised the version of FileZilla I got is more than three years old.

So I looked at the changelog starting from my version (3.15) and I found this:

  3.37.3 (2018-10-01)
    Bugfixes and minor changes:
      Fix issues with directory creation when uploading many files in
      parallel

I'm pretty sure that is the bug I'm experiencing; so apparently it is fixed upstream. Even if I'm wrong and it's not that one, it's extremely unlikely that such a critical bug wouldn't be fixed upstream by now.

This is a CRITICAL bug that renders FileZilla completely unusable.

Please update it to a decently recent version without this or other crippling bugs.
Even downgrading to an *earlier* version before the bug (I'm sure it's a regression, but I can't tell in which version it appeared) would be better than nothing.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: filezilla 3.15.0.2-1ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-148.174-generic 4.4.177
Uname: Linux 4.4.0-148-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Jun 5 22:44:59 2019
InstallationDate: Installed on 2013-10-11 (2063 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
SourcePackage: filezilla
UpgradeStatus: No upgrade log present (probably fresh install)