I had a neighbor - husband from Madrid, wife from the Canary Islands. I could understand him perfectly but her, I understood nada. Every word had a “th” sound thrown, just for the heck of it. So “eso” became “etho” and “seuerto” became “suertho”. And her talking speed was Mach 1.
That is castellano. He’s from Madrid, and SHE has the Castilian accent? That is truly weird.