Submitting BUR Form causes CookieOverflow exception

can't submit my first BUR here because of this server error.
I've tried deleting my _danbooru2_session cookie, logging out and back in, but the BUR creation always failed with this message:

An unexpected error has occurred.

Details: ActionDispatch::Cookies::CookieOverflow exception raised.

app/logical/rack_server_timing.rb:19:in 'RackServerTiming#call'

has anyone else run into this?

How long is your BUR? Is it a very long BUR? IIRC that error happens when there's so many errors that the error notice overflows and can't be displayed. If it's very long, try splitting it into multiple smaller BURs.

my BUR is very looooooooooong, so I'll try splitting it up like you said.

shortened it and now I'm getting 502 Bad Gateway message from Cloudflare repeatedtly when I try to submit. is this pure coincidence or did I break something server-side?

the Help: How to make a bulk update request guide at the top of the page said to write changes like this:

imply rabbit_tail -> tail

I followed their example exactly, and wrote many lines like this. wouldn't really expect any syntax errors. im a bit lost.

tried again and the website finally showed me the tag-related error notices. I understand what it wants now: each tag there must have its own wiki page.
the overflow explanation did help, so thank you for that.