Loading multiple Assetbundles causes a Crash

Good evening, I have the following problem: when I load an assetbundle, and then i unload everything from it and load another one and so on, mabye i only switch between 2 assetbundles the app after a while 20-30 trys on nexus 10 and a bit more on Nexus 5 crashs... but I have no Idea why.... First i thought it could be the Memory.. but i checked everything with the profiler and it looks ok. I get a Signal 11! This is a small part of it:

    #01 pc 003c9b38 /data/app-lib/com.xx.xx-1/libunity.so (std::basic_string, stl_allocator>::operator=(char const*)+20)
    #02 pc 003ca314 /data/app-lib/com.xx.xx-1/libunity.so (MemoryProfiler::RegisterRootAllocation(void*, BaseAllocator*, char const*, char const*)+108) 
    #03 pc 000b2958 /data/app-lib/com.xx.xx-1/libunity.so (set_root_allocation(void*, MemLabelId, char const*, char const*)+72)
    #04 pc 001e0454 /data/app-lib/com.xx.xx-1/libunity.so (WWW::FeedUnityWebStream(bool)+480) 
    #05 pc 004b4d34 /data/app-lib/com.xx.xx-1/libunity.so (AndroidWWW::ReadCallback(void*, void*, int, void*, int)+200)

Thanks