This is a follow up. The issue was half resolved and wanted to share with everybody.

As I tested audio recording on the same backing track many times, I found that:
- One recording was successfully in-sync, but if I recorded the same song again, it was out of sync.
-Sometimes the audio was ahead of the backing track and sometimes it was delayed.

So, it looks unstable. Every time I tried to record an audio, the timing with the backing track was ahead, delayed or in-sync.

Then, I changed Audio Driver setting from WAS (Default) to MME, and tried the same thing. So far, so good. Every time I tried to record, always the audio was in-sync with the backing track.

So, it seems that WAS has some problem in BIAB2019. The workaround is to select MME.

If any of you had similar issue, let's share with us.

Thanks