COP verification of Daikin Ururu Sarara in low-load conditions

Hi folks,

in brief I would like to compare notes on a high-end Daikin mono-split unit,
and I am wondering how kinks of various degrees would effect performance or operation in heating.

I am just examining a newly-installed Daikin Ururu Sarara 9000 btu air conditioner (FTXZ25N/RXZ25N). Since this is one of the best available units for efficient heating, I am interested in verifying its COP in part load conditions.

By the book this unit should perform with a COP of 6 in lowest part-load (100 W consumption) at 7 degrees outdoors, however I am having trouble reproducing these COP values in own measurements, whereas the performance seems adequate at higher part loads.
I am leaving out many details, since the topic of COP measurement can be a major subject on its own. Just let me note that I am comparing both with manufacturer ratings and independent benchmarks from a Finnish climate measurement lab.

Based on that I am getting unsatisfactory COP in some conditions I am looking for advanced troubleshooting.
Both refrigerant charge and installation conditions are flawless, we the exception that I cannot currently check against kinks in the pipes around one of the bends.

Therefore my question: Has any of you advice on how kinks affect performance during heating? I have little experience with this type of problem, and I wonder how it would be possible to check for that without ripping apart all the trunking and insulation.

Temperature differences before and after the suspected bend would be an interesting thing to look at, but due to the superheat of the gas coming from the outdoor unit during heating I am not so sure how useful this would be.

Looking forward to an interesting discussion :)

Cheers,
-David