My car (1.5 ADV 2018) has been having rattling problems from the back, since 1st month (February)

all this while we all thought it's suspension or absorber problem so keep wasting time (at least 15 hours so far) waiting inside SC for them to investigate, even left my car there for 4 days.

Problem never went away until last month I asked my friend to sit on the floor in my backseat to try to figure out whether sound is from inside or outside.

Turns out it's from inside, after we fold down the back seat (driver side), the sound went away.

Yesterday sent my car for 20k service and told them about it, and after checking they found out my seat bracket is loose and cannot be tightened, so need to wait 1 week for parts to arrive. Fingers crossed this will solve the problem.
Unsolved problem so far:

Rattling sound on dashboard (especially driver side, Smarttag reader there) already tried inserting card in between panel and windscreen still no improvement, took out the aircond blower also still got that sound, so the issue is deep inside behind the steering, die la. Already leave car there few days they still couldn't fix it and it got worse. paria punya burukdua, why can't i afford a better car?!!!

when I said better car I meant minimum Honda Civic    my myvi now got vios engine already, I NEED MOAR POWER

god car 50k got leaking absorber.. but since under warranty change for free.. best part about god car got free movie, free makan minum, free chilling artificial garden zone with water fountain..