Advanced Windows Files

Windows uses UTF-16 by default. Other services may use derivations there of. In any event, it's recommended to normalize things to UTF-8.  Here's a good example of what will happen if you don't;

The answer to that question is to use the specific code field, as "AUTO" doesn't seem to detect properly.

<Input in>
    Module      im_file
    File "E:/Imports/get_accessplans/log-test.txt"
    Exec if $raw_event == '' drop(); 
    Exec $Event = convert($raw_event,"UCS-2LE","UTF-8"); to_json();
    SavePos     FALSE   
    ReadFromLast FALSE

From the manual on SQL Server

Microsoft SQL Server

Microsoft SQL Server stores its logs in UTF-16 encoding using a line-based format.
It is recommended to normalize the encoding to UTF-8. The following config snipped
will do that.

<Extension _charconv>
    Module xm_charconv

<Input in>
    Module im_file
    File "C:\\MSSQL\\ERRORLOG"
    Exec convert_fields('UCS-2LE','UTF-8'); if $raw_event == '' drop();
As of this writing, the LineBased parser, the default InputType for im_file  is not able to properly read the double-byte UTF-16 encoded files and will read
an additional empty line (because of the double-byte CRLF). The above drop() call is intended to fix this.
convert_fields('UTF-16','UTF-8'); might also work instead of UCS-2LE.