ByteDance Software Engineer interview questions

I had 4 rounds of interviews. 3 technical + 1 last hr round. Coding questions are relatively easy. All technical interviews - OS, DB, network, programming language. Third round is harder compared to first 2 rounds. Interviewers are generally quite nice. The technical interview process is very fast. HR will ask me to proceed to the next round on the next day. However, after the third round of tech interview, I waited for a week to proceed with the HR round. After the HR round, I waited for 1 month to receive the final rejection email.

Was told that there will be 3 technical rounds and if passed, proceed to a final HR interview. I've did all that and out of a blue I am required to do another technical round. Who know how many more "last" rounds they would have?