What does the envoyer composer install command look like!?

We are having a very strange issue where the composer install run by envoyer fails in the scripts run with artisan (composer's post-install) with some error we cannot reproduce locally, but if we insert the same composer install command used on forge, in a hook just before the composer install run by envoyer, then it doesn’t fail. Envoyer skips it's own composer install in the output shows "skipped". We googled like madmen but never found it mentioned anywhere…. if anyone knows about this and would like to share, plz do tell! Thanks in advance for any help y’all can toss my way!

Note: We also sent a help request email via the lil’help tab on envoyer, but it’s been like a week and no response yet… Also asked on slack, but nobody has answered so far... so…. if anyone here knows… it would work to calm our burning curiosity as to why would it fail when we let envoyer run the composer install as opposed to running it ourselves just before envoyer does it…..