I had a similar experience recently but that won't help you.
During my ownership of CL9 I've had its coolant changed many times (due to one reason or another) and each time I've used Fuchs. However, the last time I had its system completely drained and filled with Honda Type 1 and subsequently got the air bled too. I've also had its radiator cleaned after I bought it, and that coupled with coolant changes means that my system is absolutely clean. I've also had its water pump pulled last year and was surprised to see that fins are in 95% condition and there is no play or sound from its bearing.
So couple of months ago I was really surprised when it started reducing coolant in the bottle ever so slightly. I knew everything was fine and despite multiple inspections, couldn't find any leak. The temp gauge was fine but OBD would show coolant temps of 110-115 even in slight stop and go drive. I had had one of the fans changed recently but still I finally inspected them and turned out that that same passenger side fan wasn't working 🤦♂️. After replacing that the temps are fine and there is no more coolant reduction.