This is a common problem that can be very disruptive to a night's sleep. I utilize the AirCurve 10 unit for bipap therapy, and have had the same issue, however I recently discovered a solution that seems to work quite well. It has completely mitigated the issue since I've implemented it.
On the unhinged side of the reservoir, there are two retention tabs that hold the lid down after you fill the reservoir with water. Once the lid gasket becomes worn in, there is a resultant loss of tension on the lid which results in it moving up/down when the pressure increases during therapy. This is what is causing the clicking noise.
To mitigate the issue, you'll need to purchase a roll of low friction, drawer slide tape. It can readily be found on Amazon, including with this link:
https://www.amazon.com/gp/product/B0BFJS...UTF8&psc=1
Cut a couple of pieces of the tape at a sufficient length to horizontally cover both tabs on the lower section of the reservoir. Fold it over so that it is adhering to the top/bottom of each tap. Repeat the process to add an additional layer of tape thickness over the tabs. Push the tape down so that it almost molds over each of the two tabs. Now, close the lid. The low friction tape will allow tab holes to slide over the tabs and then lock into place. The additional thickness of the tape on the tabs provides resistance to the lid moving up/down, and also seems to allow the tank to lock more securely in place in the AirSense/AirCurve 10.
You will probably need to replace the tape after washing the tank, but that is a simple. Hopefully, this will put an end to your sleep disruption due to the poor design of the ResMed reservoir.
