Why avatar url from oldMember and newMember are the same in a guildMemberUpdate? (Discord.js)

I'm trying to send a message in a channel when someone changes profile picture, but it's not working because url from oldUser and newUser are always the same (both are the new avatar url), I did something similar for nickname changes and it actually is working well..

bot.on("guildMemberUpdate", (oldMember, newMember) => {
    //checks if the change is the nickname
    if (oldMember.displayName != newMember.displayName) {
        console.log(`(NEW ACTIVITY): @${oldMember.user.username} changed username. @${oldMember.displayName} was the username before update, @${newMember.displayName} is the username after update`);
        //build embed
        messages.usernameUpdate(bot, oldMember, newMember);
    }

    console.log(oldMember.user.displayAvatarURL());
    console.log(newMember.user.displayAvatarURL());
    //checks if the change is the profile picture
    if (oldMember.user.displayAvatarURL() != newMember.user.displayAvatarURL()) {
        console.log(`(NEW ACTIVITY): @${newMember.user.username} updated profile picture`);
        //build embed
        messages.photoUpdate(bot, oldMember, newMember);
    }
});

logs after change profile picture, oldMember and newMember avatar url are the same (new avatar url):

https://cdn.discordapp.com/avatars/826073829302206525/4eab82e784ca3caa8ed1ba18631541b2.webp
https://cdn.discordapp.com/avatars/826073829302206525/4eab82e784ca3caa8ed1ba18631541b2.webp

Solution

I think it's a known issue and it works like this because Discord sends both PRESENCE_UPDATE and GUILD_MEMBER_UPDATE if the user information is changed.

First, on the PRESENCE_UPDATE discord.js determines the change and apply it to the cache and on the GUILD_MEMBER_UPDATE the underlying user is already changed from the PRESENCE_UPDATE so the old user cannot be emitted with the old member. So, every time a user is updated, GUILD_MEMBER_UPDATE will not hold the "old" data, just the updated version. That's the reason oldMember.user.displayAvatarURL() is the same as newMember.user.displayAvatarURL().

I know it probably wasn't the answer you were expecting.