Gee, that's weird. I just re-ran the code, no problem. writetable dates to R2013a, so that's unlikely an issue. Of course, t2 did not append becuase the 2nd writetable crashed. I really don't know what the issue. If somone else reads this and has an idea, perhaps they'll weight in.
You can also select a web site from the following list:
How to Get Best Site Performance
Select the China site (in Chinese or English) for best site performance. Other MathWorks country
sites are not optimized for visits from your location.