4k Video Downloader constantly crashes on OS X and fails to finish downloading Youtube videos

Per the title - a representative crash report follows. If it wasn't so damn buggy and I could have proven it worked, I probably would have donated to unlock the full application months ago :(

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Process: 4kvideodownloader [1978]
Path: /Applications/_Applications/*/4K Video Downloader.app/Contents/MacOS/4kvideodownloader
Identifier: com.openmedia.4kvideodownloader
Version: 4.1 (4.1.1)
Code Type: X86-64 (Native)
Parent Process: ??? [1]
Responsible: 4kvideodownloader [1978]
User ID: 502

Date/Time: 2016-07-10 20:01:43.335 +1000
OS Version: Mac OS X 10.11.5 (15F34)
Report Version: 11
Anonymous UUID: 24AE0386-1A7F-A140-FFA9-CF1DEC6A96F3

Sleep/Wake UUID: 29E2279C-49E6-4193-99B8-36C943371096

Time Awake Since Boot: 660000 seconds
Time Since Wake: 1100 seconds

System Integrity Protection: enabled

Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY

VM Regions Near 0:
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__TEXT 000000010d5e1000-000000010dccf000 [ 7096K] r-x/rwx SM=COW /Applications/_Applications/*/4K Video Downloader.app/Contents/MacOS/4kvideodownloader

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 com.openmedia.4kvideodownloader 0x000000010d9c362b openmedia::downloader::http_downloader_urls::pause() + 11
1 com.openmedia.4kvideodownloader 0x000000010d724f77 openmedia::downloader::media_downloader_lazy::pause() + 55
2 com.openmedia.4kvideodownloader 0x000000010d628c14 ViewModel::DownloadItemViewModel::onBasicAction() + 84
3 org.qt-project.QtCore 0x000000010fbe75bd QMetaObject::activate(QObject*, int, int, void**) + 749
4 org.qt-project.QtWidgets 0x00000001109de96f QAction::activate(QAction::ActionEvent) + 303
5 org.qt-project.QtWidgets 0x0000000110b5c8d2 QMenuPrivate::activateCausedStack(QVector const&, QAction*, QAction::ActionEvent, bool) + 82
6 org.qt-project.QtWidgets 0x0000000110b5a90f QMenuPrivate::activateAction(QAction*, QAction::ActionEvent, bool) + 591
7 org.qt-project.QtWidgets 0x0000000110a270b8 QWidget::event(QEvent*) + 1656
8 org.qt-project.QtWidgets 0x0000000110b60fb1 QMenu::event(QEvent*) + 1105
9 org.qt-project.QtWidgets 0