Goldman Sachs is entangled in an increasingly contentious fight over a 2014 takeover on which it advised, underscoring the treacherous legal environment for mergers and acquisitions bankers.

Goldman faces fresh allegations that it failed to spot in time, then covered up, a share-count error that shortchanged Tibco Software investors by $100 million when the company was sold last year. The lawsuit, whose allegations Goldman denies, seeks unspecified damages for Tibco investors.