Problem is: many labour MPs are from hard-brexit districts. Same thing for conservative MPs.
In fact, the problem is that the electoral map of the UK is more hard-brexit than the popular vote, while the MPs from hard-brexit districts are mostly remainers. Remainer MPs from hard-brexit districts have contradictory and irreconcilable motivations: they want the UK to remain in the EU, but they want to remain MPs. If at the end of the day the UK does not exit the EU, those MPs will lose their seats -- that's a lose-lose for them. If the UK manages to exit the EU, those MPs have a fighting chance to be reelected.
So right now Parliament wants to rescind the Article 50 invocation, but can't bring itself to say so. The best they can do without massive upheaval in the next general election is to either order a second referendum, or request a delay in exiting. And those two options only if a) the Speaker allows them (he has been allowing remainer motions that the parliamentarian has ruled out of order, so the Speaker might indeed continue to do so), b) the PM accedes or c) Parliament impeaches her. (c) hasn't happened in centuries, and (b) might not happen (but I wouldn't hazard a prediction). A successful vote of no confidence would not work: first there would have to be a new general election and a new government, which might not yield a remain result (the electoral map is hard for brexit).
Hope that makes the situation clearer, but! I am not a subject of the crown, so take this with a lot of salt.
note that you say a potential election might not yield a remain result - in fact I would suggest that it will certainly not. Even if every remain voting constituency somehow formed a government (impossible with even just SNP and Labour tensions), it would not be close to enough seats to form a government.
And the district boundaries got redrawn, and the new districts are a bit more favorable to the tories, so I think the chances of a Labour win in the next GE are only good if the tories commit electoral suicide (which, of course, they might), even assuming SNP aligns with labour (which, as you say, is not a given).
In fact, the problem is that the electoral map of the UK is more hard-brexit than the popular vote, while the MPs from hard-brexit districts are mostly remainers. Remainer MPs from hard-brexit districts have contradictory and irreconcilable motivations: they want the UK to remain in the EU, but they want to remain MPs. If at the end of the day the UK does not exit the EU, those MPs will lose their seats -- that's a lose-lose for them. If the UK manages to exit the EU, those MPs have a fighting chance to be reelected.
So right now Parliament wants to rescind the Article 50 invocation, but can't bring itself to say so. The best they can do without massive upheaval in the next general election is to either order a second referendum, or request a delay in exiting. And those two options only if a) the Speaker allows them (he has been allowing remainer motions that the parliamentarian has ruled out of order, so the Speaker might indeed continue to do so), b) the PM accedes or c) Parliament impeaches her. (c) hasn't happened in centuries, and (b) might not happen (but I wouldn't hazard a prediction). A successful vote of no confidence would not work: first there would have to be a new general election and a new government, which might not yield a remain result (the electoral map is hard for brexit).
Hope that makes the situation clearer, but! I am not a subject of the crown, so take this with a lot of salt.