Shnxx's journey

I recently accepted a conditional job offer with a multinational company and am currently in the onboarding process. However, I'm feeling anxious about my previous employment situation at IBM, where I worked for almost four years before going AWOL due to severe burnout and stress from a long commute. My employment was terminated, and I was informed that I still had a company laptop and owed around $1,300 for it and other charges. I've been unemployed for over a year, focusing on recovery and skill development, and now I'm worried that my past issues might affect the background check being conducted by my new employer. I want to know what information my previous employer might disclose during this check and if they could mention my AWOL status or the unreturned laptop. Additionally, I'm curious if a flagged issue would delay my onboarding or if the offer could be withdrawn without giving me a chance to explain. Lastly, would returning the laptop after all this time have any positive impact on how my previous employer is viewed? I'm really hoping to make this opportunity work after all the effort I've put into rebuilding my career.