Need expert for fix issue on old Android App and its Admin

Need an experienced Android App (Java) Developer with strong knowledge of (old) Rideshare App, to assist in investigating and fixing this issue. Please note that our understanding of the root cause might be completely wrong, the awarded developer must investigate all the possibilities and explain why it's happening, and implemented the required fix. You may need to check Firebase and its admin made with CodeIgniter too (if needed). details in chat.

code running well but it's some code is depricated.