Hello! Thank you for the kind words and the detailed report — and no worries at all about the translation.
We're investigating this. Two things could be going on: the multi-avatar build has a long stage where the progress display doesn't update at all (so it can look frozen while still working), but with about 10 models combined it may instead be hitting an internal size limit and failing without showing any error.
To tell which one it is, we need the log from your machine: after trying the build, please press the app's inquiry button (it has a Copy Log feature) and send it through the in-app form — that gives us everything we need to fix this.
Thanks for your patience