Duncan Borrowman and Mark Valladares have both written thoughtful pieces on how to avoid situations where the relationship between PPC and local party breaks down. Mark calls for more support for candidates. Duncan goes further by outlining some of the situations, including bullying and harrassment by small groups within local parties, that leads to selected candidates quitting.
There are two sides to this - prevention and cure. Local Parties sometimes have way too high expectations of the amount of tme a PPC can give to them - and will accept no less than 24/7. Perhaps the selection preparation should include detailed guidance to all key players in local parties about what they can reasonably expect from a PPC with similar guidance being given to approved candidates.
The easiest way to prevent tension is simply just not going to happen any time soon. At the moment, there are just too few people carrying out too many roles within the Party. We all need a bit more Party/Life balance. Burnout and stress are significant factors in relationship breakdowns. If we can't solve the problem, we at least need to be aware of it.
In terms of cure, if a PPC has resigned, particularly in a key seat, should there not be some sort of intervention to work out what has gone wrong with the aim to prevent the same thing happening again? The local party should not be allowed to select again without it and the candidate should have a long debrief. If there has been obvious fault, the party needs to have a sanction, to
Finding a way to deal with this issue sounds like a job that a full-time President of the Party could and should take on before any more good people, from both local parties and PPCs are demoralised and demotivated.