I'm using a 2018 Mac mini with macOS 10.15.4. Using the Sunday, January 12, 2020 build, if I close the main window or quit the program while live video is displayed, the program crashes after a short delay.
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x000033abb4b1c108
Exception Note: EXC_CORPSE_NOTIFY
Termination Signal: Segmentation fault: 11
Termination Reason: Namespace SIGNAL, Code 0xb
Terminating Process: exc handler [8147]
VM Regions Near 0x33abb4b1c108:
MALLOC_LARGE 00000001519f7000-0000000153591000 [ 27.6M] rw-/rwx SM=PRV
-->
MALLOC_NANO 0000600000000000-0000600008000000 [128.0M] rw-/rwx SM=PRV
Thread 19 Crashed:
0 libIvsDraw.dylib 0x00000001068cc13b DCM::CIvsPaint::DrawFunCallBack(int, void*, long) + 27
1 libvaxplayer.so 0x0000000109732185 CVaxPlayerImp::InnerDrawFun(int, void*, void*) + 101
2 libdhplay.so 0x00000001248f920b dhplay::CCallBackManager::onVideoDraw(void*, void*, void*) + 75
3 libdhplay.so 0x000000012492b581 dhplay::CCocoaOpenGL::OnDrawCallback(void*) + 55
4 libdhplay.so 0x0000000124cb15b5 -[COpenGLContextRender Render:Rect:] + 2148
5 libdhplay.so 0x0000000124cb079e CMacOpenGL::Render(DecOutputParam*, RenderRect*) + 148
6 libdhplay.so 0x000000012492b5bf dhplay::CCocoaOpenGL::Render(DEC_OUTPUT_PARAM*, __SF_RECT*, __SF_RECT*) + 13
7 libdhplay.so 0x000000012492a356 dhplay::CVideoRender::ShowMultiWindow(DEC_OUTPUT_PARAM*, int) + 222
8 libdhplay.so 0x000000012492a21d dhplay::CVideoRender::Render(DEC_OUTPUT_PARAM*, int) + 141
9 libdhplay.so 0x00000001249197c3 dhplay::CPlayGraph::OnPlayLastVideo(DEC_OUTPUT_PARAM*, __SF_FRAME_INFO*, int) + 421
10 libdhplay.so 0x000000012491989d non-virtual thunk to dhplay::CPlayGraph::OnPlayLastVideo(DEC_OUTPUT_PARAM*, __SF_FRAME_INFO*, int) + 13
11 libdhplay.so 0x000000012490f88e dhplay::CPlayMethod::PlayLastFrame(int) + 74
12 libdhplay.so 0x000000012490f11f dhplay::CPlayMethod::PlayVAFrame(int, int*) + 177
13 libdhplay.so 0x000000012490f00c dhplay::CPlayMethod::OnTimeVASync() + 124
14 libdhplay.so 0x000000012490ee78 dhplay::CPlayMethod::OnTime() + 22
15 libdhplay.so 0x000000012490c626 dhplay::CPlayTimer::RenderWorkThread() + 100
16 libdhplay.so 0x000000012490c5bd dhplay::RenderWorkThread(void*) + 9
17 libsystem_pthread.dylib 0x00007fff6846f109 _pthread_start + 148
18 libsystem_pthread.dylib 0x00007fff6846ab8b thread_start + 15
Also, if I set a PTZ preset, then delete it, a small blank window appear in the middle of the screen, behind the prompt:

- Untitled.jpg (54.04 KiB) Viewed 6899 times
After I close the prompt, the window remains. I can bring the main window forward, and I can select either window, but the small window can't be moved. It only goes away when I quit the program.