Shell content display changed issue

When issuing "less" command and using the keyboard up key to look back at the shell content, the shell content shows is changed by wrong.

WindTerm 2.5.0

e.g.

**The original content in the shell:**
```
WKDAYNOW=`date +%u`
if [ "${WKDAYNOW}" -le 5 ]
then
BACKDAYS=`expr ${WKDAYNOW} + 2`
else
BACKDAYS=`expr ${WKDAYNOW} - 5`
fi
```

FRIDAY=`date -d -${BACKDAYS}day +%Y%m%d`

**The changed content displayed when we did the action as we described above:**
```
WKDAYNOW=`date +%u`
if [ "${WKDAYNOW}" -le 5 ]
thenACKDAYS=`expr ${WKDAYNOW} + 2`
else CKDAYS=`expr ${WKDAYNOW} - 5`
fiIDAY=`date -d -${BACKDAYS}day +%Y%m%d`
```

Reproduce the issue in WindTerm 2.5.0 by displaying multi-line shell content with less, then pressing the keyboard up key to inspect scrollback. Trace the terminal display or scrollback entry point involved in that action; done means the displayed content remains identical to the original shell content.

Written by the indexing model from the issue text.