I did about a dozen orbs right after update, and I ever only do Mars, and I did get multiple loud thuds from terminal coffer.
Oh for sure! I wasn't implying it's not possible, just that it never happened to me specifically, post AMAN Trove update.
Also I can confirm everybody who said Loud Thud without Belligerent Bang. I got many myself, altough I think most (all?) of mine came from Rainbow chests.
We can't say for certain unless SE tells us, but my idea is that the chest "changes" when it becomes Rainbow.
As such we can see two different scenarios:
A) That chest was a Noise or a Thud before
B) That chest was a Loud Thud already before
For scenario A) it's only right you weren't getting Belligerant Bang.
This sort of scenario doesn't answer Pantafernando's question though, because that chest *became* a Loud Thud but it wasn't such before.
So to better rephrase Panta's question let's define a more precise scenario:
1) We're past the third opened chest
2) We're not getting Belligerant Bang message
3) No Loud Thud in the Terminal Coffer
4) No Rainbow chests
Did anybody get a loud thud in such a situation? I don't remember if it ever happened to me honestly.