Atrius97

Additional context for why the crashes were occuring:

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There are 23 stubbed items in Pokémon Scarlet and Violet that map to TM Materials for Sprigatito, Fuecoco, Quaxly, Koraidon, Miraidon, the Treasures of Ruin, and Paradox Pokémon found in the Paldea Pokédex, item IDs 2100-2102 (Sprigatito through Quaxly), 2124-2125 (Koraidon and Miraidon), 2138-2151 (Paradox Pokémon, excluding Walking Wake and Iron Leaves), and 2152-2155 (Treasures of Ruin).

If the game attempts to grant these items to the player, such as via the rewards following the completion of a Tera Raid Battle, the game will crash.

Walking Wake and Iron Leaves event raids did attempt to grant bonus drops of TM Materials, however they were unaffected by this glitch due to not having an associated TM Material item ID. 7★ raid battles for species not found in Paldea, (such as Charizard), were also unaffected, as they did not have TM Materials in the item pool.

The first instance of this glitch occurred May 19, 00:00 to 02:00 UTC, 2023 with the introduction of Great Tusk and Iron Treads event raids.

Initial post/context from @mattyoukhana_:

Explanation of the glitches with this event via Bulbapedia:

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This event was originally intended to run between May 19, 00:00 UTC to May 21, 23:59 UTC, 2023, but included two notable glitches during its initial introduction on May 19, 2023:

• The item rewards attempted to grant and display TM Materials for Great Tusk and Iron Treads, despite both species not having associated TM Material items. This caused the item rewards screen for some players to display "None" as one of the item rewards, followed by the game crashing.^[7][8]
• All Iron Treads raids with random Tera types were erroneously coded never to appear as Shiny,^[9] despite both versions of Great Tusk, and the Iron Treads with the forced Ground Tera type being able to appear as Shiny at the standard 1:4103.05 odds.

At approximately 02:00 UTC on May 19, 2023,^[4] all event raids were removed from the server, (including the 7★ Chesnaught the Unrivaled event), replaced with completely blank event data for any players that connected during this time. The official Japanese twitter account issued an apology,^[5] but the event was eventually announced as being cancelled entirely.^[6] This is the first instance of a Poké Portal News event being removed from the server entirely to address a glitch.

Image of the glitched "None" TM Material items, prior to game crash:


Additionally, an announcement for a 7★ Delphox event running from May 26, 2023 00:00 UTC to May 28, 2023 23:59 UTC briefly appeared in the Pokémon HOME calendar on May 21, but was removed almost immediately, likely due to the cancellation of the prior event causing scheduling conflict:

s.

As of 2021-12-23, the Icy Snow Vivillon in Box 24 is illegal, due to the Country/Sub Region not matching the form, (Icy Snow form is not obtainable in Tokyo, Japan).

The PID generation method and RNG conditions of My Pokémon Ranch are at-time-of-writing unknown. Like all other Hayley trades, this is likely to be shiny-locked, and no one has ever come forward with proof of receiving a shiny Hayley Mew or Phione, but a shiny-lock has never been confirmed for sure.

Edit: Kurt, Sabresite, and Admiral-Fish discovered Ranch uses antishiny ARNG, which is the same method that causes Gen 4 Mystery Gift anti-shininess.
https://bulbapedia.bulbagarden.net/wiki/Pseudorandom_number_generation_in_Pokémon#Alternative_pseudorandom_number_generator_.28ARNG.29

The PID generation method and RNG conditions of My Pokémon Ranch are at-time-of-writing unknown. Like all other Hayley trades, this is likely to be shiny-locked, and no one has ever come forward with proof of receiving a shiny Hayley Mew or Phione, but a shiny-lock has never been confirmed for sure.

Edit: Kurt, Sabresite, and Admiral-Fish discovered Ranch uses antishiny ARNG, which is the same method that causes Gen 4 Mystery Gift anti-shininess.
https://bulbapedia.bulbagarden.net/wiki/Pseudorandom_number_generation_in_Pokémon#Alternative_pseudorandom_number_generator_.28ARNG.29

As a note, this is not legal if distributed to Japanese Emerald specifically. 

Source: https://github.com/kwsch/PKHeX/issues/3040

As a note, this is not legal if distributed to Japanese Emerald specifically. 

Source: https://github.com/kwsch/PKHeX/issues/3040

This encounter actually can be reached directly after the Gladion Battle at the base of Mount Lanakila.

The Rainbow Rocket arc does not need to be completed for this.