The bug is sliding up a hill (using 255 speed and 80 gravity in a private server).
This bug happens on every attempt.
I play on PC.
Step 1: Own a private server/have a friend on who owns one, and have the gravity set to 80 and your speed to 255.
Step 2: Go to the hill outside and to the left of Row 3, particularly on the part of this hill to the right of the tunnel through it.
Step 3: Run up the hill, holding jump the whole time.
Not a GUI bug.
Roblox User: RobloxRavager507.