With the example below and the latest beta (2017.07.14 19:35), I get the following error whenever a bold face is requested:

lua error       > lua error on line 44 in file C:/Users/rik/Desktop/test/prod_quotation.tex:
...ext/tex/texmf-context/tex/context/base/mkiv/font-ots.lua:5336: attempt to index local 'one' (a boolean value)

The typescript in the example is based on the delivered typescript with the replacement of bold fonts by semibold. This has worked in the past with no problems.

(Is there a way to accomplish this without replicating the whole of the typescript?)

\starttypescript [serif] [libertinus]
    \setups[font:fallback:serif]
    \definefontsynonym [LibertinusSerif-Regular]
       [file:libertinusserif-regular]
    \definefontsynonym [LibertinusSerif-Italic]
        [file:libertinusserif-italic]
    \definefontsynonym [LibertinusSerif-Slanted]
       [file:libertinusserif-italic]
%   \definefontsynonym [LibertinusSerif-Bold]
%      [file:libertinusserif-bold]
%   \definefontsynonym [LibertinusSerif-BoldItalic]
%      [file:libertinusserif-bolditalic]
%   \definefontsynonym [LibertinusSerif-BoldSlanted]
%      [file:libertinusserif-bolditalic]
    \definefontsynonym [LibertinusSerif-Bold]
       [file:libertinusserif-semibold]
    \definefontsynonym [LibertinusSerif-BoldItalic]
       [file:libertinusserif-semibolditalic]
    \definefontsynonym [LibertinusSerif-BoldSlanted]
       [file:libertinusserif-semibolditalic]
\stoptypescript
\starttypescript [serif] [libertinus] [name]
    \setups[font:fallback:serif]
    \definefontsynonym [Serif]
        [LibertinusSerif-Regular]
        [features=default]
    \definefontsynonym [SerifItalic]
        [LibertinusSerif-Italic]
        [features=default]
    \definefontsynonym [SerifSlanted]
        [LibertinusSerif-Slanted]
        [features=default]
    \definefontsynonym [SerifBold]
        [LibertinusSerif-Bold]
        [features=default]
    \definefontsynonym [SerifBoldItalic]
        [LibertinusSerif-BoldItalic]
        [features=default]
    \definefontsynonym [SerifBoldSlanted]
        [LibertinusSerif-BoldSlanted]
        [features=default]
    \definefontsynonym [SerifCaps]
        [LibertinusSerif-Regular]
        [features=smallcaps]
\stoptypescript
\definetypeface[mainface][rm][serif][libertinus][default]
\setupbodyfont [mainface]
\starttext
    Text
    \bf bold text
\stoptext

--
Rik