HmIP-eTRV-B-2 valve oscillation

[RudyM]

I am having an installation with 10 groups, a CCU3 with Raspberrymatic. The groups are configured:
8 groups: HmIP-eTRV-B-2 + HmIP-WTH-1
1 group: 2x HmIP-eTRV-B-2 + HmIP-WTH-1
1 group: 3x HmIP-eTRV-B-2 + HmIP-WTH-1
The installation is working fine except for the two multi HmIP-eTRV-B-2 groups. The valves of these groups are oscillating on a few minutes base between two relatively close values, for example: 11% and 15% opening. It seems that Homematic IP is having troubles with multiple HmIP-eTRV-B-2 groups.
I tried to reconfigure the groups or to cut the direct binding of the two HmIP-eTRV-B-2 . Nothing seems to help.

Any suggestion for a solution.