On Windows, I got it working again with current Context (20180404) and current luatex from win32tex
(1.07 development ID 6686)

On linux-armhf I did a fresh "./first-setup.sh --engine=luatex" and got:

mtx-context | ConTeXt Process Management 1.02
mtx-context |
mtx-context | main context file: /usr/local/context/tex/texmf-context/tex/context/base/mkiv/context.mkiv
mtx-context | current version: 2018.09.30 19:32

and:

This is LuaTeX, Version 1.09.0 (TeX Live 2019/dev)

The LuaTeX team is Hans Hagen, Hartmut Henkel, Taco Hoekwater, Luigi Scarso.

LuaTeX merges and builds upon (parts of) the code from these projects:

tex : Donald Knuth
etex : Peter Breitenlohner, Phil Taylor and friends
omega : John Plaice and Yannis Haralambous
aleph : Giuseppe Bilotta
pdftex : Han The Thanh and friends
kpathsea : Karl Berry, Olaf Weber and others
lua : Roberto Ierusalimschy, Waldemar Celes and Luiz Henrique de Figueiredo
metapost : John Hobby, Taco Hoekwater, Luigi Scarso, Hans Hagen and friends
pplib : PaweĊ‚ Jackowski
fontforge : George Williams (partial)
luajit : Mike Pall (used in LuajitTeX)

Compiled with libpng 1.6.35; using 1.6.35
Compiled with lua version 5.3.5
Compiled with mplib version 2.00
Compiled with zlib 1.2.11; using 1.2.11

Development id: 6930

No experimental, i think.

Am 2. Oktober 2018 07:12:02 MESZ schrieb luigi scarso <luigi.scarso@gmail.com>:


On Tue, Oct 2, 2018 at 7:03 AM Lutz Haseloff <lutz.haseloff@toppkieker.info> wrote:
Hi Hans, hi all,

I think, that recent context has a problem with scaling included pdf files.
My minimal file:

\startMPpage
draw externalfigure "cow.pdf" ;
\stopMPpage

The resulting pdf is, as the original, 97x70.6 mm, all ok.

If I try to scale to the original size, i get arithmetic overflow error.

\startMPpage
draw externalfigure "cow.pdf" xscaled 97mm yscaled 70.6mm ;
\stopMPpage


Whe i scale it down, the pdf gets really big.

\startMPpage
draw externalfigure "cow.pdf" xscaled 27.5mm yscaled 20mm ;
\stopMPpage

results in a pdf with width of 4.938,8 mm and height of 2.612,3 mm.

I tested with recent context and luatex under windows 64 and linux-armhf.

which context and luatex version ?  Are you using experimental ?
--
luigi