xshell lag when execute shell script [1]

I have a very simple shell script:
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#!/bin/bash

#echo "1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1"
for i in {1..23}; do printf "1."; done

start=$(date +%s)
read -p "input a char:" user_ack
echo ">>>: $user_ack"
end=$(date +%s)
echo "time:$((end-start))";
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When execute this in xshell, the xshell UI will lag for a while, if change the 23 in for circulation to a larger number, the lag time will be longer.
This an odd appearance to me, and I try this script in other shell client, it work with expectation, desktop terminal is OK too.
Last, I try this script in xshell 5, it's no lag.
So, what is the problem with my script?

Program Ver. : Xshell 6

We believe this may not be a common issue. Our tests showed no errors or log when executing this script.

Therefore, the issue seems to be related to something else which we will continue to investigate.

Technical Support

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