Welcome to the Community @brianbrennan
I suspect that is somewhat out of scope for Choice’s focal activities but there are numerous posts on the Community about experiences, and your comments seem germane to ‘Choosing a builder’ so I merged it here.
Other than surveys and compilations of complaints that usually get to ‘he said she said’ discussions, calling in engineers and surveyors, and sometimes silks, doing more than a ‘how to guide’ would be a very significant endeavour, with this topic being no more than a primer on the possible things that could get overlooked or go pear shaped.
Having had some experience with a significant commercial build that was managed under questionable circumstances as well as having been a student of ‘media reports’ over time, there are known to have been (and probably remain) some commercial and probably residential builders who are masters of low balling a bid to get a job and then negotiating up for every meeting, letter, email, and variation that arises to achieve a top profit before it is over. About 20 years ago I seem to remember a builder got disqualified from government bidding for a few years for that practice.
There are also known dodgy practices whereby builders delayed completing a development to hit the sunset clauses so they could renegotiate or cancel a contract since ‘the price is up’ or the ‘size of the flat is down’ to make more of them; government finally took notice of that but I do not know if the outcome was as efficacious as it could have been.
When it happens it can be largely on those who write the specifications that are not ‘tight enough’, or sometimes the customer or contract manager as they feel random changes should just be done, whether or not required by the contract.