Citi Senior Software Developer interview questions

There were 3 rounds. L1(2 coding, others are based on core java) L2(1 coding, other are related to project and linux based some scenario) L3(Managerial) Explain the gap throughout your education and jobs. The process was fast intially they took first 2 rounds on weekend then last one after 4-5 days. When it came to result. They gave me two reason why I am not selected. 1. Stability(As per my resume, It is already mentioned that i have multiple switches for some reason but why they shortlisted if it is the issue. I didn't get.) 2. Don't know much unix commands(I have answered each question correctly related to the unix commands. but didn't know what they are expecting.)