Pretty cool animation, and surprisingly smooth for 13FPS. I do see some artifacting here and there, but I think that might be a flipaclip problem.
Never heard of flipaclip before. Though, if you want to use a different program to animate I have a few alternatives for Mac and PC:
Krita is nice program that's mainly used to draw, but it can also be used for basic traditional animations. It's a bit weird since it feels like photoshop with an animation timeline, and it's a bit of a heavy program too so it may not run smoothly all the time when animating, but the option is there.
Pencil2D is a janky yet simple and lightweight program that's able to do both traditional and vector animations...with the only problem being that you essentially only have MS-Paint tools to work with (minus the text tool). It's kinda bad, and you need to find workarounds if you make complicated animations, but maybe it's a step above flipaclip? i don't know.
Never tried adding audio in either program. I don't think Krita supports audio, but I know that Pencil2D has that feature, but the devs recommend using a video editor for sound mixing instead since they admit their program is terrible with audio. Something like OpenShot is probably good enough to do the job.
All of these programs are free, so you can try them yourself to see if you like them.
Hope this helps! ...Even if my tools aren't much better honestly.