The top of the stack trace is exactly the same as before, except for the new name for "b".
buffer-substring-no-properties(nil 6747)
(cons (buffer-substring-no-properties (cadr pairs) (car pairs)) acc)
(setq acc (cons (buffer-substring-no-properties (cadr pairs) (car pairs)) acc))
(while pairs (setq acc (cons (buffer-substring-no-properties (cadr pairs) (car pairs)) acc)) (setq pairs (cddr pairs)))
(let ((pairs (cons e (append @-holes (list vc-rcs--b)))) acc) (while pairs (setq acc (cons (buffer-substring-no-properties (cadr pairs) (car pairs)) acc)) (setq pairs (cddr pairs))) (apply (quote concat) acc))
(The next line of the backtrace has 159030 characters, most of which are from the master file. Sorry again that I can't provide an example, but the file doesn't belong to me.)