"Pos," apparently the Cuban accent is the remnant of Spaniards from the Canary Islands, who settled in Cuba. They, too, treat middle consonants in a similar fashion.
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.