x <- c("/en/house/125,/en/house/145,/en/house/06", "/en/house/45,/fr/house/22,/fr/house/34", "/es/do/45,/ro/nu/22,/ja/hs/34")
gsub("(^|,)/[a-z]{2}/", "\\1", x)
eCA8LSBjKCIvZW4vaG91c2UvMTI1LC9lbi9ob3VzZS8xNDUsL2VuL2hvdXNlLzA2IiwgIi9lbi9ob3VzZS80NSwvZnIvaG91c2UvMjIsL2ZyL2hvdXNlLzM0IiwgIi9lcy9kby80NSwvcm8vbnUvMjIsL2phL2hzLzM0IikKZ3N1YigiKF58LCkvW2Etel17Mn0vIiwgIlxcMSIsIHgp