I have a real problem with Jamie Driscoll, the incumbent North of Tyne mayor, being blocked from standing again. It is clearly due to internal, petty factionalism.
It's due to the fact that he interviewed Ken Loach, expelled from the party, at a theatre in Newcastle a couple of months ago, to discuss films produced in the North East, and not about anti-semitism, Israel / Palestine etc. Clearing appearing on the same stage as someone does not mean that you share their views. It has clearly also been done in an undemocratic way, with no right to appeal.
Interestingly Alistair Campbell, so not exactly a Corbynite on the left of the party, strongly disagrees with the move, as does Andy Burnham who I'd say falls under the 'soft left' bracket. Driscoll appears to be a very well liked mayor, and has been effective at reaching out across the political spectrum to do what is best for the people he represents, including trying to work constructively with the Tory Tees Valley mayor Ben Houchen.
Clearly it's important to view these matters on a case by case basis, and not through a 'left vs. centre' tribal basis. During the Corbyn years for example, I vehemently disagreed with the treatment of Luciana Berger and though that the attempted motion of no confidence in her was a disgraceful, while on the flipside I thought that the attempted motion of no confidence in Margaret Hodge (who smeared and slandered Corbyn and was clearly undermining the party even encouraging people to vote against it ahead of the Euro elections which was far worse than Campbell saying he voted for the Lib Dems after polling closed) was 100% justified.