While evaluating the form starting at line 33, column 0
  of #P"/usr/local/share/maxima/5.41.0/share/pdiff/pdiff.lisp":

debugger invoked on a SB-INT:BUG in thread
#<THREAD "main thread" RUNNING {10006105B3}>:
    failed AVER: (NOT (SB-C::CTRAN-NEXT SB-C::CTRAN))
  This is probably a bug in SBCL itself. (Alternatively, SBCL might have been
  corrupted by bad user code, e.g. by an undefined Lisp operation like
  (FMAKUNBOUND 'COMPILE), or by stray pointers from alien code or from unsafe
  Lisp code; or there might be a bug in the OS or hardware that SBCL is running
  on.) If it seems to be a bug in SBCL itself, the maintainers would like to
  know about it. Bug reports are welcome on the SBCL mailing lists, which you
  can find at <http://sbcl.sourceforge.net/>.

Type HELP for debugger help, or (SB-EXT:EXIT) to exit from SBCL.

restarts (invokable by number or by possibly-abbreviated name):
  0: [RETRY       ] Retry EVAL of current toplevel form.
  1: [CONTINUE    ] Ignore error and continue loading file "/usr/local/share/maxima/5.41.0/share/pdiff/pdiff.lisp".
  2: [ABORT       ] Abort loading file "/usr/local/share/maxima/5.41.0/share/pdiff/pdiff.lisp".
  3: [MACSYMA-QUIT] Maxima top-level
  4:                Ignore runtime option --eval "(cl-user::run)".
  5:                Skip rest of --eval and --load options.
  6:                Skip to toplevel READ/EVAL/PRINT loop.
  7: [EXIT        ] Exit SBCL (calling #'EXIT, killing the process).

(SB-C::LINK-NODE-TO-PREVIOUS-CTRAN #<SB-C::REF  :LEAF #<SB-C::GLOBAL-VAR :%SOURCE-NAME ERROR :TYPE #1=#<SB-KERNEL:FUN-TYPE (FUNCTION ((OR # # BASE-STRING FUNCTION SYMBOL CONDITION SB-PCL::CONDITION-CLASS) &REST T) NIL)> :DEFINED-TYPE #1# :WHERE-FROM :DECLARED :KIND :GLOBAL-FUNCTION {1003886C13}> {1003886EA3}> #<SB-C::CTRAN 1 {1003877B83}>)