I am using the latest version of the plugin myself (4.2-RC1.3). Besides other trouble I have (see here in the forum) and the general problem of a lack of development, I cannot reproduce your problem.
I use the shortcode like this:
[standings league_id=14 season=2015-16]
and it filters the season accordingly. You have to make sure to get the ID right and that the season code is set up exactly like you use it in your shortcode.
In a previous post the season was set to [standings league_id=1 logo=true season=2017-18-P1]. This showed the correct standings.
After creating a new season 2017-18-P2 this morning, the same shortcode in that same post now shows the standings for 2017-18-P2 instead of 2017-18-P1.
So, the ID was never changed (I’m still looking at the same old post which wasn’t updated) yet the result is not what it used to be before adding the new season!
Try the most simple shortcode and see if that still works. Maybe the parameter logo is no longer supported? I never used it.
Try [standings league_id=1 season=2017-18-P1] and see if that works.
