Bug Report - Gen 3, changing to second ability.

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Describe the bug
After transfering Pokemon between Generation 3 games, abilities will change to the second ability for some Pokemon in a given save, even if they were not transfered (on FireRed and Emerald).

Expected behavior
I have transfered Pokemon between Emerald and FireRed several times, at some point some abilities changed and would appear as having no ability.

Screenshots

I have not used PKHex to interact with these saves at any point, other than to show that some Pokemon appear as illegal, due to their ability.

Information about your environment

• PKSM version: Various (the most recent versions from late 2023 to early 2024)
• Entrypoint: Luma CFW

Additional context
I can send the save files if needed.