Confirmed - cause found, patch not written yet.

On a steep enough slope the grounded check throws away the floor you are on once the per-frame rise exceeds 3px, and the landing check then refuses to catch you again.

Moving it out of OPEN so the list reflects reality: this one is pinned down to exact files and lines, so what is left is writing and testing the change, not working out what is wrong.

Fixed - commit 7794a3e2, in the next build.

Same root cause as #81, fixed in one change: the per-frame ground check could not recognise the floor you were already standing on, so on a steep enough slope it dropped you instead of letting you walk up. It now holds on to your current floor while you are still above it, matching the original client.

The slope you found in Henesys is one of 4,029 across the game that were steep enough to hit this.