High cpu usage of the cmc process

We added 2 cpu cores, however after some time (ca. 1.5h) the cmc process uses again ca. 100% of the one core. Really strange. Interesting is also that the restart of the cmc process “cmk restart cmc” is not enough. Only “cmk -R” or “omd restart siite” commands are able to lower the cpu usage of the cmc process.
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Has anybody a similar issue?