Evening chaps...
When the last signal before a station is a long block, the train simply decelerates on the last station tile (instead of in steps across the last three station tiles).
Here's a simple save to demonstrate (pak64):
https://www.dropbox.com/s/u8g0u5o5k570e24/bug.sve?dl=0
This has been around since at least r8356.
The bug should be fixed in r10124.