1. Start a fresh emacs by 'emacs -Q' in terminal
2. Enable chinese-py input method of quail by eval'ing below snippet:

    (setq default-input-method "chinese-py")
    (toggle-input-method)

3. Start defining keyboard macro by hitting 'F3'
4. Input Chinese '你好' by typing 'ni1hao1' in the '*scratch*' buffer,
    and end keyboard macro by 'F4'
5. Replay keyboard macro by 'F4', it will get '嗯你h好', which is *not*
    exactly the same.
6. 'M-x kmacro-edit-macro' shows that some characters('n' and 'h') are
repeated:
    ;; Keyboard Macro Editor.  Press C-c C-c to finish; press C-x k RET to
cancel.
    ;; Original keys: nni1hhao1

    Command: last-kbd-macro
    Key: none

    Macro:

    nni1hhao1 ;; self-insert-command * 9

7. My guess is that it's due to put back the key into
'unread-command-events' in the function 'quail-start-translation', i.e.:
    (if key
        (setq unread-command-events (cons key unread-command-events)))

In GNU Emacs 26.1 (build 1, x86_64-redhat-linux-gnu, GTK+ Version 3.22.30)
 of 2018-06-26 built on buildhw-10.phx2.fedoraproject.org
Windowing system distributor 'Fedora Project', version 11.0.11906000
System Description: Fedora release 28 (Twenty Eight)

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading quail/PY...done

Configured using:
 'configure --build=x86_64-redhat-linux-gnu
 --host=x86_64-redhat-linux-gnu --program-prefix=
 --disable-dependency-tracking --prefix=/usr --exec-prefix=/usr
 --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc
 --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64
 --libexecdir=/usr/libexec --localstatedir=/var
 --sharedstatedir=/var/lib --mandir=/usr/share/man
 --infodir=/usr/share/info --with-dbus --with-gif --with-jpeg --with-png
 --with-rsvg --with-tiff --with-xft --with-xpm --with-x-toolkit=gtk3
 --with-gpm=no --with-xwidgets --with-modules
 build_alias=x86_64-redhat-linux-gnu host_alias=x86_64-redhat-linux-gnu
 'CFLAGS=-DMAIL_USE_LOCKF -O2 -g -pipe -Wall -Werror=format-security
 -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions
 -fstack-protector-strong -grecord-gcc-switches
 -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1
 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic
 -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection'
 LDFLAGS=-Wl,-z,relro
 PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GSETTINGS NOTIFY ACL
LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 MODULES THREADS XWIDGETS LCMS2

Important settings:
  value of $LC_CTYPE: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny seq byte-opt gv
bytecomp byte-compile cconv dired dired-loaddefs format-spec rfc822 mml
mml-sec password-cache epa derived epg epg-config gnus-util rmail
rmail-loaddefs mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils quail help-mode easymenu cl-loaddefs
cl-lib elec-pair time-date mule-util tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow isearch timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese composite charscript charprop case-table epa-hook jka-cmpr-hook
help simple abbrev obarray minibuffer cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote dbusbind inotify lcms2 dynamic-setting system-font-setting
font-render-setting xwidget-internal move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 99183 11721)
 (symbols 48 20740 1)
 (miscs 40 58 129)
 (strings 32 36203 1462)
 (string-bytes 1 794714)
 (vectors 16 15442)
 (vector-slots 8 509842 12640)
 (floats 8 49 201)
 (intervals 56 296 7)
 (buffers 992 12))