slime-autodoc stops working after some time

Hi,

 after some time slime-autodoc stops working on my machine. I haven't
yet found out what triggers this. Disabling/Reenablinging
slime-autodoc-mode doesn't help. It works again after restarting emacs
and lisp.

Here is the situation after it stops working:

- Calling #'slime-arglist directly works: The symbol at point is
  suggested correctly and the arglist is properly displayed.

- <C-h k SPC> displays:

  SPC runs the command slime-autodoc-space (found in
  slime-autodoc-mode-map), which is an interactive Lisp function in
  =E2=80=98slime-autodoc.el=E2=80=99.

  It is bound to SPC.

  (slime-autodoc-space N)

  Like =E2=80=98slime-space=E2=80=99 but nicer.

  [back]

- Running #'slime-autodoc-space manually results in a ^M displayed at
  point.

This is on emacs 26.1, slime 2.21, sbcl 1.4.8, Arch Linux 64 bit.

Can someone help or give me some hints how to debug this?

--
Orm