[pedvide]

There are a lot of "temporary" internal border checks within Schengen [1], especially in the last 5 years. Wiki has lots of info [2]

I've personally been checked in trains crossing from the east towards Germany multiple times, including the night train.

1. https://www.reddit.com/r/MapPorn/comments/17yy61g/current_re...

2. https://en.m.wikipedia.org/wiki/Schengen_Area under "regulation of internal borders"