Hi @Sketchy, I think you are not alone with this one 
Krita wont fully render the animation
Animation export bug in latest release
If so, t’s a known bug and it’s been reported: 459993 – Frames being named incorrectly and program being unable to found specified frames to being encoded
Please check/confirm that your animation can Render from frame-0 to frame-something.
Read this reply for a crude workaround:
Krita wont fully render the animation - #6 by AhabGreybeard