This is a common part of the acquisition process. If notable irregularities are discovered upon "opening up the books", a deal may be renegotiated or either side could decide to back out. Even after the Twitter deal was tentatively approved at $54.20/share, the stock remained below $50 and is now around $40 in pre-market trading. Meanwhile, Tesla stock had dropped around 36% since Musk announced his 9.2% purchase of Twitter.