I wanted to try your mode and at the same time installed the [url=https://mods.factorio.com/mod/trainConstructionSite] Train Construction Site mod[/url],

When I placed the first Trainbuilder block I got this error:

The mod How Far Has it Been? caused a non-recoverable error.
Please report this error to the mod author.

Error while running event howfardiditgo::on_nth_tick(30)
LuaTrain API call when LuaTrain was invalid.
stack traceback:
howfardiditgo/control.lua:68: in function <howfardiditgo/control.lua:65>
stack traceback:
[C]: in function 'index'
__howfardiditgo/control.lua:68: in function <howfardiditgo/control.lua:65>

Would you please look into it ?

Hmm I can guess the cause of this, I'll have to download the mod and see how to workaround it (if it's even possible)

I'll see if I can make some time to look at it in the next couple of weeks.

has any headway been achieved towards fixing this?

Finally took a look at this today. It was only semi-what I was expecting the issue to be. However, this is fixed in 0.17.5.

Let me know of any odd behaviours that still appear. I've only done first-pass testing to make sure trains created via this mod are tracked and the data is kept tidy. There's some bugs in the Train Construction mod which also complicated things a bit, so as those are fixed it may cause others to pop up here.