I have the desribed problem on two devices with the same luatex (development id 6832) and context beta 2018.06.25.
Debian jessie (armv7l) on xperia z1 with Android 7 (Gnuroot Debian) and
Debian stretch (armv8l) on galaxy a6 with Android 8 (UserLAnd)
$> context test.tex &>out-context
should give something like
$> head -1 out-context
mtx-context | run 1: luatex --fmt="/opt/context/experimental/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luatex/cont-en" --jobname="test" --lua="/opt/context/experimental/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luatex/cont-en.lui" --no-parse-first-line --c:currentrun=1 --c:fulljobname="./test.tex" --c:input="./test.tex" --c:kindofrun=1 --c:maxnofruns=9 "cont-yes.mkiv"
and then running
$>luatex --fmt="/opt/context/experimental/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luatex/cont-en" --jobname="test" --lua="/opt/context/experimental/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luatex/cont-en.lui" --no-parse-first-line --c:currentrun=1 --c:fulljobname="./test.tex" --c:input="./test.tex" --c:kindofrun=1 --c:maxnofruns=9 "cont-yes.mkiv"
we should have more info
--
luigi