Mr. Corbyn represents the people who elect the Labour leader. Labour MP's represent the people who elect the Government.
Who is Mr. Corbyn leading? A Left Wing pressure group or Her Maj's elected Parliamentary Opposition?
I think enough MP's are smart enough to realise that Mr. Corbyn will never represent an electable Labour Government. Ergo he is in the wrong job. He isn't the leader of the parliamentary Labour Party. I can't see that he even understands what that Job is.
The way he is handling the ISIS issue makes this impasse abundantly clear. Perhaps even to Dandelion.
The responsibilities of a UK MP are set out. They have responsibilities towards two or three groups:
1) Constituents
2) Parliament
3) Party (if any).
The first two are linked. The MP represents the interests of their constituents (not just those that voted for them) in parliament; their responsibility to parliament is to debate, scrutinise and vote to represent the interests of parliament. The responsibility of MPs to their Party is of a lower order. There is plenty of protocol around country not party.
There is of course the situation where most MPs are elected on a party ticket and therefore with a party manifesto. It is often reasonable for an MP to argue that the party manifesto is the interest of the constituents. It is problematic however when a political party makes major changes in their manifesto after an election.
The Corbyn changes are such that the Labour party is advocating a set of economic, social, defence and foreign policies totally at odds with the manifesto on which Labour was elected. This puts MPs in a bind. There are options for them as individuals: they could become independents, or they could join another party whose present policies more closely represent the Labour manifesto on which they were elected. I appreciate these are not good options. It would be coherent for Labour MPs to resign in mass and fight by-elections on their new manifesto. It would also be coherent to say that the policy change of the opposition is of such a magnitude that a new general election is needed. This is problematic with the Fixed Term Parliament Act. However it could be triggered by an agreement of Conservative and Labour, or with Conservative plus 104 MPs (to make 2/3rds of parliament). I don't see that Labour would see this in their interest right now.
Presumably Labour will have a go at ousting Corbyn. They need a candidate, and they need to be sure Corbyn doesn't get 20%+ of the Parliamentary Labour Party backing him (surely he wouldn't, but it is a risk). The new Labour leader would need to set about kicking out the Marxists, Leninists, Trotskyites, Communists, friends of terrorists and various lunatics - a hard job.
If Labour fail to oust Corbyn they need to break away and form a New Labour party. In such a circumstance it may suit them to support a General Election in order to give them legitimacy. They would be without the debts and assets of Labour, which may have advantages.