War ended with cancellation (Crusader Kings 3)

Hello, I play for Ireland. started from the Duke, knocked together the whole country, a powerful dynasty of managers, a lot of money.
To the point:
1) He invited his cousin-in-law, the uncle of the King of England, to the court (he has a claim to the Kingdom of England).
2) Concluded the matrilineal engagement of his granddaughter with their eldest son (he is the same 3 years old), took him under guardianship.
3) Prepared the economy and the army for war and declared war for the son-in-law's claim.

The plan is this: put a son-in-law on the throne, his son will inherit his throne (by that time the husband of the granddaughter by matrilineal marriage)
- as a result, the great-grandson will become a member of my dynasty and inherit both kingdoms and, as a result, create the British Empire.

Problem.
I win the war up to about 70 percent. Knocks out such a communication - the war is cancelled. tried to capture faster or smash the troops first, the effect is always the same... Writes The King (Actual) of England does not have the titles for which the claim is submitted, but remains the King of England further.

Is this a bug? or I don't understand something?
thanks for the help