[details=“English Translation”]After so many problems, it seems that Juan has lost his mind.
[/details]
According to the RAE, you can use chaveta as a synonym for loco:
chaveta
Del it. dialect. ciavetta, it. chiavetta.
adj. coloq. loco (‖ que ha perdido la razón). Se ha vuelto chaveta.
Sin.:
loco, enloquecido, tronado, revirado, locuaz, ñampeado.
https://dle.rae.es/chaveta