Thanks. That seems to work if I delete the entry in custom dictionary.

However, only if I deliberately capitalise the first letter when I start a sentence with the word - then it auto-corrects to lower-case

- Matteo needs help. = matteo needs help.

If I write it with the first letter in lower case, it corrects to upper-case!

- matteo needs help. = Matteo needs help.

If there is a way around this, that would be perfect, if not then I suppose the instruction to users would be to always write the word with an uppercase "M". Then this would solve the issue.