It is a font setup problem. Remove your font definitions and fallbacks and change
\setupbodyfont[mainface]
to \setupbodyfont[dejavu] for the start (it will cover greek and cyryllic, too).
Can you describe what you need? Are the requirements given (main font,
scripts, serif & sans, fallbacks fonts to other scripts)?
For example
IBM Plex will cover most of what you need (except cjk for now) and there is a font definition file
type-imp-plex.mkiv
in the distributio
n (not all fallbacks defined, yet).
Regards,
Jano