"Introduction of a new SAP system"
Which should have set alarm bells ringing from day 1.
Note. SAP has been supplied in various "pre-configured" versions set up for best practice (at least SAP think its best practice) in various industrial sectors.
Pre-load on new servers, bring them in on a weekend, Upload historical data to new servers and your ready to go Monday morning. It *can* work.
*Provided*
SAP have a version for your business sector (local govt?).
Your way of working maps to SAP well (or can be made to).
You've done *serious* work on data mapping your existing systems to SAP's and cleaned the data *before* you do the transfer.
You've made proper arrangements to handle the *complete* ETL process, starting with a *full* backup of all your core systems.
And in the case of *multiple* local govt bodies they *converge* there business processes into a *single* path to eliminate all that "If council = little-dunny-on-the-wold then set majority to Conservative" special case coding.
What's the betting they got the full fat swiss-army-knife SAP version with *lots* of bespoke coding (at full contractor rates)?
Note an SAP financial system delivered to NASA gave *unified* accounts across all its sites for the first time *ever* and identified roughly $876Bn in misaccounted money dating back to the founding of the Agency. NASA used to have the same auditors as Enron. They don't anymore. See CFO magazine for details.