Hi,

Looks like it is a problem with "StartPage" and "StopPage" in metapost.

I get the same error with any MP graphic using those commands.

More minimal example (without simpleslides) as per the wiki:

https://wiki.contextgarden.net/Cover_Pages

colors          > 'rgb' color space is supported
colors          > 'cmyk' color space is supported
fonts           > preloading latin modern fonts (second stage)
fonts           > 'fallback modern-designsize rm 12pt' is loaded
metapost        > initializing instance 'metafun:1' using format 'metafun' and method 'default'
metapost        > loading 'metafun' as '/usr/share/texmf/metapost/context/base/mpiv/metafun.mpiv' using method 'default'
metapost        > initializing number mode 'scaled'
input stack overflow
mtx-context     | fatal error: return code: 256

Commenting out "StartPage" and "StopPage" compiles.

mtx-context     | current version: 2021.05.09 17:14

This is LuaTeX, Version 1.14.0

Development id: 7438