Hi Kahliekc,
I think I found the problem.
Can you open your sbs in Designer and switch to SSE2 engine ? (hit F9 and choose SSE2)
Now set the resolution to 4k, this way you should get the same result as in Unreal.
I tested this on my side and all the cracks disappear. They are probably too thin to be seen in Unreal.
Other possibility, you use a flood fill node which only works in GPU mode.
Feel free to send us your sbs if you want us to confirm this. (Use private message if you prefer)
Thanks !