you're probably facing some rendering issues. the sex scenes were always a clusterfuck. the game is "complete" in that the author threw up their hands, told everyone to fuck off and left. the mods heard them cry "I'm done with this bullshit" as they rode into the sunset, and so marked the game complete instead of abandoned.
yes, the game is essentially 2d
don't expect any bugfixes to come down the pipe for any of the weird shit, hangs, bad graphics or broken features.
all that said, while I haven't played it in a while, I did play it quite a bit while it was still in development. Yes, the author walked away while it was still in a pretty buggy state, but this software was a huge undertaking. It was cool of the author to try for something so large and complex in the first place.
I just glanced at their patreon, looks like they're doing a stationmaster 2.0. it's likely that 1.0 was just too much of a pain to work in, since they would have been writing exploratory code to get where they did, it was inevitably filled with hacks and work arounds and structures that ended up working against new features and fixing bugs. hopefully they have a better run of it this time. I guess you can go support them if you're interested in a redone version of the game.