Alan Bowen schrieb am 30.04.2021 um 13:19:
> Hi, Wolfgang—
>
> I copied all the fonts to a new document (file attached) and ran 
> ConTeXt. The problem persists. The cause, I think, comes in the lines:
>
> \definefallbackfamily[mainface] [mm] [STIX Two Text]
> [range=digitsnormal,
> force=yes,
> features=f:oldstyle]
> which used to give me oldstyle numerals.

I'm unable to reproduce the error with your example and most of the 
fallbacks are ignored because I don't have the fonts.

To ensure there is no problem with the format and font database delete 
the cache and rebuild it:

         mtxrun --script cache --erase
         mtxrun --generate

When this doesn't help you simplify your example. First remove one 
\definefallbackfamily at a time and afterwards remove \definefontfamily 
until the error disappears.

Wolfgang