Owner CFO financials vs GAAP

The most common century old anomaly, all brokers, investment banks and brokers are well aware of the difference, but by nature of required 'known amnesia' they forget to report the difference early on.

Here is what happens:
We all go in a deal believing the seller/CFO/CPA (to the extent of Baker Tilly Review Engagement reports)/investment banks aka glorified brokers that the financials presented are aligned with GAAP, means revenue, ebitda, cost recognitions are managed by qualified team who understands the GAAP project management principles, and no fake ebitda/revenue/low cost estimates have been added in to bluff up numbers (they now feel offended if you call it bluff, albeit I call it bluff, you BS 60 years old owner/CFO with $3m ebitda getting review engagement done by Baker Tilly has obviously mislead financials to buyers, because I will not believe BK does not know the GAAP for project based/construction industry recognition principles).

My question is: what processes, questions/checklists do you absolutely adhere to before taking deal into LOI to ensure the above does not trick you in the deal/dd?

Because this difference, unlike Addbacks are far harder to deal with as metrics will drop significantly by over 50% at any given day, if the GAAP is misled to you.

What precautionary steps do searchers take early stage, pre-LOI and $ costly dd?