LattePanda Sigma: issues with thermals and fan noise

Hi,

as the title suggest, I'm looking for some help on a LattePanda Sigma 32GB (DFR1090) regarding thermals and fan noise.

The issue:

While perfectly happy with its advertised specs (it's a beast and fun to work with) the claim "Rapid Chill, Silent Whisper" has failed utterly for me. For me it's so bad that I'm even considering returning or selling it again.

Sure when idling it's (basically) dead silent, but with even as little as 10-15% of "sustained" load (>2min) or a quick! CPU spike of over ~30% and the fan will ramp up significantly and on a noise level, depending on the ambient noise, that still can be heard in the next room. (And the Sigma is in a closet!). Doing a simulated stress test with 100% load and the fan will scream at you.

With no specific fan or CPU setting altered (apart from boot everything is in on default), in the closet, at idle, the CPU reports an average temperature of 50-55°c.

Same scenario, but outside the closet and at an ambient temperature of ~23°c, average CPU temps are 45-50°c. Of course it stays cooler/quieter for a bit longer, but not much. The general problem persists.

Putting the Sigma in its official "Vertical M.2 Expansion Support Case" definitely helps to reduce the threshold for the fan to ramp up, but again only a little.

Of course, factoring in its size and performance, I'm not expecting the Sigma to stay dead silent on 100% sustained load, but comparing to a Dell XPS 15 9510 laptop with similar performance, its screaming loud. Especially on a "normal" usage.

Can anyone confirm this issue or has a solution for it?

Should I consider re-pasting or is the cooling solution just (utterly) undersized for its TDP (and the "Silent Whisper" claim)?

If the later, has anyone successfully swapped out the stock cooling and has recommendations on what to use instead?