I really hate working with learning management systems (LMS).
I make training simulations for retail companies and some of these have the worst, backwards LMS's out there.
The providers who install and manage these LMSs for the companies always insist we make our training run inside their own environment, but we can't since it's a 3D training made in Unity that doesn't run well in a browser.

Luckily some of these are fine to figure out. Just a few API calls here and there for authorization and reporting progress, but some are an absolute nightmare.

Just now one of the providers provided me with a 2000 page documentation of all the functions of the LMS's API that our customer is using. All I need are like 5 pages that explain what URL to call with what data and the responses, but now I'm stuck spending days trying to find the 0.5% of this documentation that I need to communicate with their API.

And of course, the documentation is vague as all hell. minimal descriptions of what each endpoint does. Subjects names are super vague, as in do I look for course progress or lesson completion state. What the heck is a Learning Event, is it relevant to me?

And the errors in this document, too.
Bullet-point lists with duplicate items.
language errors everywhere.
Property lists where they copy-pasted the description of properties.
An entire EMPTY chapter, literally a page with only the chapter's title.

I just can't stand how these providers barely seem to know anything about the API of the LMS's they provide to customers.
(for clarity, the LMS is produced by some big tech company, it's installed and maintained by some 3rd party which is our main line of communication when rolling out trainings to these).

It always goes like: "Hey, we want to use your training." "Oh, that's great, we have our own, simple LMS where you can view your employee's progress." "Nah, we want to use our backwards LMS. Here's a giant manual about it's API, go figure it out!"
And then I'm left here tearing my hair out trying to figure out which 3 calls I need to send their API from the tons of extra stuff it can do which is completely unnecessary and being unable to rely on the provider because they lack the knowledge and have such thick skulls about the implementation of the LMS itself that they also seems completely unwilling to help to begin with!

Just another day at the office.