The Citizens Advice Bureau here have just put up the post linked below re overstaying your 90d in 180d. Also worth checking is their link to the EES Entry Exit System process being wheeled out in advance of ETIAS.
Consequences of Overstaying in Spain? Fines or Expulsion
Information is added for you almost on a daily basis. We are a charity with no external funding. Any amount you are willing to donate will be greatly appreciated. The following are serious offenses: a) Being found irregularly in Spanish territory, due to not having obtained the extension of...
www.citizensadvice.org.es
Protected: EES/ Entry-Exit System. Border Control and Identify Over-Stayers
At present, the stamping of passports, biometrics and additions to a database are used for border control. The Entry/Exit System (EES) will be an automated IT system for registering travellers from third-countries, both short-stay visa holders and visa exempt travellers, each time they cross an...
www.citizensadvice.org.es