Nvwgf2umx.dll leaves running threads after closing NVENC

Hello! If I use NVENC, it creates some internal nvwgf2umx.dll threads. But if I close the encoder (I use nvEncDestroyEncoder and cuCtxDestroy for CUDA device), the threads are still there and running.
If I recreate the encoder several times in a row, it can create more threads. The number of threads is fixed on 39 after recreating the encoder multiple times. Though the number doesn’t grow further, the threads are still there and I can’t remove them.
Is it possible to close the encoder in a way to close the nvwgf2umx.dll threads?

I’m mostly concerned about NVFBCAsyncThread which doesn’t close. The most interesting part is that I don’t use the async encoding param (so _NV_ENC_INITIALIZE_PARAMS::enableEncodeAsync is 0 for me). I checked and the thread is still there whether I use the async mode or not.