(See my previous post about n-back words)  I found only two in English: beriberi, hotshots. There are some more in Hungarian: előkelők, tisztiszolga, történetének.  It’s addictive, don’t read this post before going to bed.
I really can’t stop, I just checked if there are words with an amazingly repeating block of 5 letters.  None in English, only one in Hungarian: tisztességesség.