Planet Senior Backend Engineer interview questions

Engineers in the company seemed fine. However the HR/Hiring department was extremely unprofessional. After 8 interviews and a task I was told I had an offer (with salary details etc. given) and there was just a call to discuss contract details left. Then I was informed that the team had actually a couple followup questions on the task. In that call I was immediately rejected by engineering manager. The hiring manager never messaged/called to explain or apologies. Also the whole process was extremely haphazard, often with stages being "forgotten" and no details given along the way. Big red flags.