A situation like this can be frustrating but the basic steps to take are the same as for any case of professional negligence.
Make sure that you have all of the paperwork on file for each of the advisers — contracts, written agreements, specifications, schedules of work, etc. Prepare a written record that shows the services provided by each adviser, when those services were supplied and what went wrong.
Taking legal advice, particularly in cases where different advisers are disagreeing about your claim, should help to clarify the issues and highlight the most effective legal route to take.