Should i pay relocation costs during a significant integration/reorganization

My previous company is asking me to repay 50% of relocation costs and 100% for the signing bonus since i left after 19 months. I signed a pretty standard contract during the offer process with a 100% repayment clause for the 1st year and 50% the sec. The Company went through major integration: doubled size from 30 000 people to 60 000 people.2 main points: 1) Organization set up took 10 months to be defined...still not completely which could have eliminated my role and
2) My role/scope and responsibilities changed significantly (more than 50%) but was never asked to accept this new position

Could i claim a constructive discharge based on 1) the risk it created on my job to be eliminated and the need for me to sustain the needs of my family
2) the change of role and responsibilities that makes the first offer connected to the relocation obligations obsolete?