Sliding doesn't work with the latest plus.
The rabbit won't crouch unless it's completely stopped.

Old plus:
https://imgur.com/a/jj2-5-9-slide-sn7ydYl
New plus.
https://imgur.com/a/jj2-6-2-no-slide-fbPHfqj

i discovered the same, and i had the same problem, that Sliding doesnt worked for me
for some reason, that i dont know yet whats wrong,
.
its absolutly strange, i think it must be a bug
because sometimes, i can Slide, and then in a other server it dont works to Slide
.
today i discovered :
when i start my own server , here i can't Slide, and if i join my own server, i also found out, the players 2,3........ also can't Slide,
but when i join "Puke Nuk3m Arena 1 " its strange ? here it worked. to Slide
and when i joined "Puke Nuk3m Battle " here Sliding doesnt worked
i know, it dont sounds beliveable
but it really happend
means, in some servers here i can slide, and in the other server it dont worked ?
..so whats wrong ?
.
with Sliding i mean if you run with your rabbit on maximum speed, and just hold on.
=
here your rabbit should Sliding.. for a short time
means the rabbit should slide a few blocks forward (and also should show a hold on animation*),
.
if the sliding doesnt works, when you run on maxium speed, and just hold on, then your rabbit hold on in this moment, and dont have any slide effect
i also discovered if sliding doesnt works, if you run and hold on, you also can not look down
means,
if you run on maxiumum speed, and just hold on, you cant look down, it only works to look down , if your rabbit stopped moving.. and its standing
.
*
//jazzSD: animation from Lori
Set ID: 62
Animation: 60
.
Animations: 58 and 59 , 60 <- open jazzSD, and take your focus on this animations, if your bunny run with maximum speed and you just hold on, are this animations also missing for you?
.
and if Sliding doesnt works, suchs animations is missing, if you running fast and, hold on
if sliding doesnt works you also can not look down, it only works if your rabbit is not moving anymore and standing
.
do anyone have seen this too?
i mean, if it works to Slide, and then the other time, it dont works, this must be a bug
im not sure, does anyone know here more?

i also told from my experience, that there was servers where Sliding worked, and in the most other it dont works, also in my own server it dont worked to Slide.

its me again!!, i found something out, i must tell about it
.
i told from my experience, that in "Puke Nuk3m Arena 1" the Slide works,
and in other servers, i made the experience that Slide doesnt works
.
so i thought that this server where it works, must run a mutator, that make Slide possible again!
=
i was right!! about it
+ that server have a mutator running that bring the Slide effect back.
.
1. create a new file, and name it to: stvoldslope.mut
2. add this code:

#pragma name "Toggle old slope physics"

bool stickyByDefault = false;
bool suppressSlopeCommand = true;

enum oldslope_packetType { setSticky, getSticky };

void setSlopeSticky(bool sticky, bool dontSendPacket = false) {
    jjPlayersStickToSlopes = sticky;

    if(!dontSendPacket) {
        jjSTREAM packet;
        packet.push(uint8(setSticky));
        packet.push(sticky);

        jjSendPacket(packet, 0);
    }

    if (jjIsServer)
        jjConsole(">> |||Slope sticking " + (sticky ? "|||||ENABLED" : "||||||DISABLED"), true);
}

void onLevelLoad() {
    if (jjIsServer)
        jjPlayersStickToSlopes = stickyByDefault;
    else {
        waitingForResponse = true;
        jjSTREAM packet;
        packet.push(uint8(getSticky));
        jjSendPacket(packet, 0);
    }
}

bool onLocalChat(string &in stringReceived, CHAT::Type chatType) {
    if (stringReceived == "!slope on") {
        setSlopeSticky(true);

        return suppressSlopeCommand;
    }

    if (stringReceived == "!slope off") {
        setSlopeSticky(false);

        return suppressSlopeCommand;
    }

    return false;
}

bool waitingForResponse = false;

void onReceive(jjSTREAM &in packet, int clientID) {
    uint8 type;

    if (packet.pop(type)) {
        if (type == setSticky) {
            bool stick;
            if (packet.pop(stick))
                setSlopeSticky(stick, waitingForResponse);
        } else if (jjIsServer && type == getSticky) {
            jjSTREAM newPacket;
            newPacket.push(uint8(setSticky));
            newPacket.push(jjPlayersStickToSlopes);

            jjSendPacket(newPacket, clientID);
        }
    } else {
        jjConsole("> Failed to pop packet from client #" + (clientID + 1) + " (one-indexed)");
    }
}

.
3. start your own server on local,
4. say this command: /mutators stvoldslope.mut on
5. with this mutator, it Bring back the Slide effect (if anyone need it)
.
when the mutator is running, you can try out commands like:
!slope on
and
!slope off
.
just test it out, and look what happend
when your rabbit is running with maximum speed, and you just hold on,
if you made "!slope on" then it doesnt works to slide
if you turn "!slope off" then it works to slide
this also have effect for all players in your server
.

Thanks Fabian, that's helpful. When jjPlayersStickToSlopes is true, the skidding animations don't display, and also sliding doesn't work. This started in 5.12c, but will take some thought to figure out how to fix...