I customized horizontal auto-scrolling like this:
hscroll-margin set to 1,
hscroll-step set to 1 (tested with 2, same effect).
display-line-numbers-width set to 3
display-line-numbers set to t

When hscrolling starts, it goes ok for 4, 5 chars then buffer jumps to
the beginning of the line (i.e. hscroll resets) and cursor disappears.
Can still hscroll with keyboard though (cursor remains somewhere on the
right, not visible).

In GNU Emacs 26.0.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
of 2017-07-15 built on home
Repository revision: 8b64a80a56c0e15d3313a45022ae60b33dbb4bff
Windowing system distributor 'The X.Org Foundation', version 11.0.11903000
System Description:      Ubuntu 17.04

Configured using:
'configure --without-pop --with-mailutils'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GCONF GSETTINGS NOTIFY ACL
LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 LIBSYSTEMD

Important settings:
  value of $LC_MONETARY: en_US.UTF-8
  value of $LC_NUMERIC: en_US.UTF-8
  value of $LC_TIME: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Emacs-Lisp

Minor modes in effect:
  paredit-mode: t
  flyspell-mode: t
  rainbow-mode: t
  diff-hl-flydiff-mode: t
  diff-hl-mode: t
  diff-auto-refine-mode: t
  highlight-numbers-mode: t
  hl-todo-mode: t
  global-auto-revert-mode: t
  delete-selection-mode: t
  yas-global-mode: t
  yas-minor-mode: t
  global-flycheck-mode: t
  flycheck-mode: t
  global-paren-face-mode: t
  paren-face-mode: t
  show-paren-mode: t
  global-auto-complete-mode: t
  auto-complete-mode: t
  projectile-mode: t
  auto-insert-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message dired dired-loaddefs format-spec
rfc822 mml mml-sec epa derived epg gnus-util rmail rmail-loaddefs
mm-decode mm-bodies mm-encode mailabbrev gmm-utils mailheader sendmail
mail-utils help-fns radix-tree crm cus-edit wid-edit tabify misearch
multi-isearch colir fill-column-indicator tempo company-oddmuse
company-keywords company-etags company-gtags company-files company-capf
company-cmake company-xcode company-clang company-semantic company-eclim
company-template company-css company-nxml company-bbdb alchemist
alchemist-macroexpand alchemist-company alchemist-help
alchemist-complete company-dabbrev-code company-dabbrev
alchemist-refcard alchemist-phoenix alchemist-compile alchemist-iex
alchemist-message alchemist-hooks alchemist-hex alchemist-mix
alchemist-info alchemist-goto alchemist-scope alchemist-eval
alchemist-interact alchemist-server alchemist-execute alchemist-report
alchemist-test-mode alchemist-project alchemist-file alchemist-key
alchemist-utils company elixir-mode pkg-info url-http tls gnutls url
url-proxy url-privacy url-expand url-methods url-history mailcap
url-auth mail-parse rfc2231 rfc2047 rfc2045 mm-util ietf-drums
mail-prsvr url-cookie url-domsuf url-util url-gw nsm puny lisp-mnt epl
elixir-smie smie pcase vc-git powerline powerline-separators
powerline-themes server paredit flyspell ispell rainbow-mode color
diff-hl-flydiff diff diff-hl vc-dir ewoc vc vc-dispatcher diff-mode
highlight-numbers parent-mode hl-todo yatemplate settings
settings-editing settings-reloading autorevert filenotify settings-langs
lang-elixir lang-php lang-cl lang-css lang-erlang ivy-erlang-complete
async counsel jka-compr esh-util swiper erlang ivy delsel ivy-overlay
ffap lang-js js2-refactor js2r-paredit js2r-conveniences
js2r-conditionals js2r-wrapping js2r-functions elixir-yasnippets
yasnippet flymake js2r-vars js2r-iife js2r-formatting js2r-helpers s
js2-mode js sgml-mode dom cc-mode cc-fonts cc-guess cc-menus cc-cmds
cc-styles cc-align cc-engine cc-vars cc-defs imenu lang-go settings-keys
settings-indent settings-backups settings-modes mode-iedit iedit
iedit-lib multiple-cursors-core rect mode-diff-hl mode-rainbow
mode-flycheck flycheck-credo flycheck cl-extra json map find-func
help-mode subr-x dash mode-flyspell mode-slime ac-slime
slime-indentation slime-cl-indent cl-indent slime-fancy
slime-trace-dialog slime-fontifying-fu slime-package-fu slime-references
slime-compiler-notes-tree slime-scratch slime-presentations bridge
slime-macrostep macrostep slime-mdot-fu slime-enclosing-context
slime-fuzzy slime-fancy-trace slime-fancy-inspector slime-c-p-c
slime-editing-commands slime-autodoc slime-repl slime-parse slime etags
xref project arc-mode archive-mode noutline outline easy-mmode pp
hyperspec browse-url mode-ido ido mode-paren-face paren-face
mode-paredit mode-paren time-date paren mode-elixir mode-erlang mode-js2
mode-web-mode web-mode disp-table mode-ac auto-complete-config
auto-complete popup settings-ui smooth-scroll deeper-blue-theme
settings-packages paths edmacro kmacro projectile advice grep compile
comint ansi-color ring ibuf-ext ibuffer ibuffer-loaddefs thingatpt
autoinsert cus-start cus-load finder-inf tex-site rx slime-autoloads
info package easymenu epg-config url-handlers url-parse auth-source
cl-seq eieio eieio-core cl-macs eieio-loaddefs password-cache url-vars
seq byte-opt gv bytecomp byte-compile cconv cl-loaddefs cl-lib 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 dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty
make-network-process emacs)

Memory information:
((conses 16 541399 74393)
(symbols 48 51468 2)
(miscs 40 1878 781)
(strings 32 156267 3755)
(string-bytes 1 7798246)
(vectors 16 57958)
(vector-slots 8 1076531 17982)
(floats 8 3361 1089)
(intervals 56 7323 3598)
(buffers 976 31))