Weird rendered result (overlapping image sequence)

Excuse me, I have a png transparent image sequence. But it got weird result when rendered, like the image is stacking each other and video was cutted (duration decreased) or something like that I’m not sure. It rendered properly in preview mode though

It should rendered like this:
But it rendered like this:

Here is the terminal output of the process video:
(I just realize that the terminal is cropped ath bottom of the video, T_T)

Synfig ver 1.2.1 (just downloaded this morning GMT+7) but it aslo happened in my synfig 1.2.0
--------- neofetch output:

OS: Antergos Linux x86_64 Model: X456UQ 1.0 Kernel: 4.12.10-1-ARCH Uptime: 2 hours, 37 mins Packages: 1657 Shell: zsh 5.4.2 Resolution: 1920x1080, 1366x768 DE: Xfce WM: Xfwm4 WM Theme: Paper Theme: Deepin [GTK2], Arc [GTK3] Icons: Numix-Circle [GTK2], Paper [GTK3] Terminal: xfce4-terminal Terminal Font: Source Code Pro Medium 12 CPU: Intel i5-6200U (4) @ 2.800GHz GPU: Intel HD Graphics 520 GPU: NVIDIA GeForce 940MX Memory: 3393MiB / 7884MiB

i use imagick for this:

convert *png out.gif