I think Split is confused by being given the same separator character twice...

HCL Notes/Domino 8.5 Forum (includes Notes Traveler)

Subject:

While the Help isn't as clear as it could be, Split isn't meant to work with a single separator consisting two or more characters. It's meant to work like the formula @Explode function, where each character in the separator argument is treated as another separator.

Re-read this part from the Help, noting the section I've bolded:

delimiter

An optional scalar String

containing the characters to separate substrings

. If delimiter is not specified, then the space character " " is used

Basically, it's trying to treat your S="##" as two separators, and apparently can't handle the fact that both separator characters are the same.

If you want "#" as a separator, just use one, like S="#".
If you must use a 2-character separator, write a custom function to do it instead of using Split.

Feedback response number SLES87C2K7 created by ~George Umboosicheketsi on 07/14/2010