Emacs 26 is unable to restore an previously saved eieio object.
Same receipt work fine in emacs 25.3

emacs-26 --batch -l eieio-fail.el produces:
Wrong number of arguments: #<subr stringp>, 3

where emacs 25.3
Loading /usr/share/emacs/site-lisp/site-start.d/autoconf-init.el (source)...
Loading /usr/share/emacs/site-lisp/site-start.d/cmake-init.el (source)...
Loading /usr/share/emacs/site-lisp/site-start.d/desktop-entry-mode-init.el (source)...
Loading /usr/share/emacs/site-lisp/site-start.d/git-init.el (source)...
Loading /usr/share/emacs/site-lisp/site-start.d/rpmdev-init.el (source)...
Loading /usr/share/emacs/site-lisp/site-start.d/systemtap-init.el (source)...
[eieio-class-tag--eieio-fail "tmp-25.3.1" nil nil #s(hash-table size 65 test eql rehash-size 1.5 rehash-threshold 0.8 data