Weird issue with E flats on Bass Tab (2.4.2)

[Michael T. Garrison Stuber]

Greetings!

        I'm hitting a strange issue with Lilypond 2.4.2.  The following works 
just 
fine:

frag =  { 
        \key bes \major
        \time 3/4
        { r2. r r r4 r c g,2 e,4 e,4 f, g,~g, a, bes,~bes,  c2 d2. ees
        r r r r 
        }
}
        
\context Staff  <<
        \context Staff { \clef bass \frag }
        \context TabStaff <<
                \set TabStaff.stringTunings = #'(-5 -10 -15 -20)
                \frag   
         >>
>>

However, if I put in change the Es to E-Flats:

frag =  { 
        \key bes \major
        \time 3/4
        { r2. r r r4 r c g,2 ees,4 ees,4 f, g,~g, a, bes,~bes,  c2 d2. ees
        r r r r 
        }
}
        
\context Staff  <<
        \context Staff { \clef bass \frag }
        \context TabStaff <<
                \set TabStaff.stringTunings = #'(-5 -10 -15 -20)
                \frag   
         >>
>>

I get the following error:

GNU LilyPond 2.4.2
Processing `SawYouNeverBassTab.ly'
Parsing...
Interpreting music...
SawYouNeverBassTab.ly:2:15: warning: Junking event: `KeyChangeEvent':
        \key bes \majo
                      r
Backtrace:
In unknown file:
   ?:  0* [lilypond-main ("SawYouNeverBassTab.ly")]
In /usr/share/lilypond/2.4.2/scm/lily.scm:
 337:  1* (let* ((failed #) (handler #)) (for-each (lambda # #) files) ...)
 339:  2* [for-each #<procedure #f (f)> ("SawYouNeverBassTab.ly")]
In /usr/share/guile/1.6/srfi/srfi-1.scm:
 652:  3  (if (null? rest) (letrec ((lp #)) (lp list1)) ...)
    ...
 656:  4  (begin (f (car l)) (lp (cdr l)))
 657:  5* [#<procedure #f (f)> "SawYouNeverBassTab.ly"]
In /usr/share/lilypond/2.4.2/scm/lily.scm:
 341:  6  [catch ly-file-failed #<procedure #f ()> #<procedure #f (key arg)>]
In unknown file:
   ?:  7* [#<procedure #f ()>]
In /usr/share/lilypond/2.4.2/scm/lily.scm:
 341:  8* [ly:parse-file "SawYouNeverBassTab.ly"]
In /usr/share/lilypond/2.4.2/ly/init.ly:
   7:  9* (if (pair? toplevel-scores) (ly:parser-print-book parser #))
   8: 10  [ly:parser-print-book #<my_lily_parser  > #<Book>]

/usr/share/lilypond/2.4.2/ly/init.ly:8:3: In procedure list-ref in expression 
(ly:parser-print-book parser (apply ly:make-book $defaultpaper ...)):
/usr/share/lilypond/2.4.2/ly/init.ly:8:3: Argument 2 out of range: 4


Anybody have a clue? I get the same error if I drop the commas and try to use 
\relative, though the problem goes away if the E-flat is higher up the staff.  
It looks like a bug to me, but maybe I'm just doing something stupid.  Help!

-- 
Michael T. Garrison Stuber
<:3 )~