How to create MPEG-DASH variants at resolutions where one dimension is not a whole number in pixels?
The scale filter resets the sample aspect ratio to match the original display aspect ratio. You should add setsar=1 after each scale. In any case, videos don't contain pixel count with fractional components, and FFmpeg won't output those.

I'm not sure about DASH but I suppose the validator expects each variant to have the same exact aspect ratio. In your command list, I can see 640x290 and 1280x582, which are not the same aspect. If DASH needs all to be same, the latter should be 1280x580