Pagdi System Case

We have an office in Mumbai which is in pagdi system building. The building is under the name of a company called M/S Deora Bros which was initial proprietorship but on 16 March 2000 its proprietor entered into a partnership with me as a partner. In May of 2001, the other partner in the partnership had retired from the firm formally leaving the company M/S Deora brothers to me, since he left the partnership firm, I became the sole proprietor of M/s Deora's brothers and hence got complete possession of the office. The Leasie of the building filed a case of unlawful transfer of property against me and my ex-partner as according to him my ex partner sub let the property to him without informing the leasie . But we did not partake in any transfer. The property received rent receipts in the name of M/s Deora brothers (the company) and is still recieves electricity bills in the same name . Since I became the sole proprietor of the company, the property came under me. Also, the plaintiff filed a lawsuit more than 14 years after I got the possession of the office and it's been in my continuous occupation since.I wanted to know your opinion if there's a legit case here or on what grounds should i make my case.