Why does my menu with select fail the first time?

I tried to answer another SO question with a simple menu using the builtin select statement. The code displays names from /etc/passwd, and let you select a name by giving a number:

PS3="Enter a number: "
select name in $(cut -d: -f1 /etc/passwd) ; do
   if [ -n "${name}" ]; then
      break
   fi
   echo "Sorry, please enter a number as shown."
done
echo "Entry from passwd is: ${name}"

The works fine except for the very first time. When you give a correct answer the first time it will ask you to try again.
I tried to get a more detailed explanation of the first time, but I couldn't get a reproducable cook-book. When you copy-paste this code on your server, and give a correct answer you will probably have the same problem. When you repeat the command (from history or a new paste), the code shows now problem. I tried to get the problem again by logging out and logging in (sometimes it works) or rebooting.
I tried different ways to reproduce the problem in other situations (using different variable names, unsetting variables, using a slow list of values with select name in $(echo One; sleep 1; echo Two; sleep 2; echo Three; sleep 1); and opening a new shell.

I searched for other examples with select, but I can't find clues in other posts like https://stackoverflow.com/a/16750755/3220113 and https://askubuntu.com/a/1716.

I tried to fix my code with a sync and that seems to be a work-around:

PS3="Enter a number: "
select name in $(cut -d: -f1 /etc/passwd) ; do
   # is sync needed here?
   sync
   if [ -n "${name}" ]; then
      break
   fi
   echo "Sorry, please enter a number as shown."
done
echo "Entry from passwd is: ${name}"

I couldn't reproduce the error when I include the sync command. Is sync really a working patch and why do I need this here?

I do not need other ways to write a menu. I already found the graphical dialog Dialog from bash script and was looking for a simple replacement of my own over-complicated https://unix.stackexchange.com/a/115371/57293.