There are no confirmed issues with a specific Pokemon blocking progression, and the only confirmed progression blocks related to items are with Key Items and Mega Stones, either by cheating them in before they are meant to be acquired in the story or failed to be added to the player inventory because of the "Items Don't Change" code.
If the issue you are encountering is an infinite load screen, disable all of your cheat codes, run whatever Recovery Code is present in your cheat file (and if there isn't one, learn to read instructions), then backup your save and run it through this save recovery tool:
https://pl.azalea.sh/
The most common cause of infinite load screen that has been reported is the use of the speed up cheat codes, often times left active through repeated saves and reloads without using the required recovery codes. There is a chance your save is corrupted and unrecoverable.