DFM opens hundreds of HTTP connection on OAS randomly

In our configuration (Agile 9.2.2.2 , clustered OAS 10.1.2.3.0 , DFM@Win) sometimes we see lots of HTTP connections opened on OAS host dedicated for DFM communication. There is no clean reason of this and we cannot put any workaround or fix at the moment. In normal situation HTTP connections stays at 20-60 level, but during such stress moments it raises up to 2000 or more.Sometimes it is able to clear by itself, sometimes it lasts for day etc.  There is no simple connection between e.g. users on system at this moment, any error visible on DFM either OAS side, no