[ONE Q&A, Help & Troubleshooting] Timmmmaaahh!:
Would you like some fries with that? ... This is part of the ROM AFAIK so flashing a different ROM may or may not change this animation (depending on which one the dev implemented).

That's because the update server for OPO has been buried (while it was still very much alive, actually). Not to worry, you can do this manually.

Note: Even though data loss should not occur using the following steps, do make proper backups before proceeding! Things can always go wrong. Make sure you have a full battery before you continue. Verify MD5 hashes on every downloaded file, the hashes are available on every download page (if you don't know how, Duck it).

Okay, I'm known for pretty big posts but I'm keeping this as rookie friendly as possible, just bare with me. If you just want the latest official release, you'll need to get to cm-13.1.2 (ZNH2KAS3P0). It should be as simple as flashing one zip but if that fails, I'll provide a few more solutions.

First things first: download and install Google's platform tools.

Mirrors to the official files you'll need can be found in this thread (I can't check if they still work right now, get back to me on that). Let me summarize for you:

Download cm-13.1.2-ZNH2KAS3P0-bacon-signed.zip and copy it to the root of your internal storage (/sdcard), you don't need any root access to write there. Just use any file explorer.

Turn your OnePlus One device off.

Boot to recovery by pressing the keys 'Volume DOWN' & 'Power' together (hold them for about 5 seconds, then let go and you'll see 1+ recovery appearing shortly after).

Flash the zip you've copied earlier (forgive me, I forgot how 1+ recovery looks like, I've been using custom recoveries for too long) and look for "install" or something, then you should be able to navigate to the zip.

All done!

Depending on how friendly official updating is, these simple steps may or may not have worked. If they didn't, incremental updating may the way to go for you. In that case, you'll need to take the steps above but instead of flashing one zip, you'll need to flash 5 of them. Since your starting point is YOG7DAS2K1, you need to flash these files in exactly this order:

YOG7DAS2K1 -> ZNH0EAS2JK: cm-bacon-cee4e8702d-to-64003595ee-signed.zip

ZNH0EAS2JK -> ZNH2KAS1KN: cm-bacon-64003595ee-to-ced5430fc0-signed.zip

ZNH2KAS1KN -> ZNH2KAS254: cm-bacon-ced5430fc0-to-9f339bddf2-signed.zip

ZNH2KAS254 -> ZNH2KAS2X1: cm-bacon-9f339bddf2-to-3c3f0aca9b-signed.zip

ZNH2KAS2X1 -> ZNH2KAS3P0: cm-bacon-3c3f0aca9b-to-2b5f277d1c-signed.zip

Download all of them first and copy all of them to the root folder of internal storage. You should be able to flash them all in one session but if that fails, try rebooting in between (boot to the Android system, turn off again and boot back to recovery, flash next zip and repeat).

Still unlucky? Then we'll have to go in the hard way! Here's the full guide for rooted users, I'll briefly explain it to you here.

Note: The steps below this point WILL WIPE ALL DATA (including app data, photos, videos, contacts, etc.). You do not need to unlock your bootloader at any point. However, if you do and you re-lock it, unlocking it again may permanently brick your device (tip: never use a batch to perform commands).

Okay, here we go (I hope you didn't get to this point but it's here just in case)...

Download this file if you own a 64GB device or this file if you own a 16GB device and extract the files within to the same folder as fastboot.exe on your computer.

Turn your OnePlus One device off.

Boot to fastboot mode by pressing the keys 'Volume UP' & 'Power' together (you'll see "fastboot mode" appearing).

Connect your OnePlus One to the computer with a reliable USB cable (a cheap cable may cause data corruption).

Flash all files by entering these commands one by one:

fastboot flash modem NON-HLOS.bin
fastboot flash sbl1 sbl1.mbn
fastboot flash dbi sdi.mbn
fastboot flash aboot emmc_appsboot.mbn
fastboot flash rpm rpm.mbn
fastboot flash tz tz.mbn
fastboot flash LOGO logo.bin
fastboot flash oppostanvbk static_nvbk.bin
fastboot flash recovery recovery.img
fastboot flash system system.img
fastboot flash boot boot.img
fastboot flash cache cache.img
fastboot flash userdata userdata_64G.img (or userdata.img if you have a 16GB model)
fastboot reboot

There, fresh as can be.

Alternatively, you can also switch to OxygenOS (also official, also no need to unlock bootloader or root). There's an official guide here.

This will probably be the most complete reply you'll ever get, lol. Nonetheless, don't hesitate to fire any questions if any should remain. Good luck! :fingers-crossed: