After calculating Radiosity iterations baking lightmap is freeze on 0%.

Hello everyone.
Here is the problem - after calculation radiosity iterations (according to Swarm log) baking of Lightmap freeze on 0%.
Moreover, loading of CPU falls from 70% to 20-30% and seems like nothing happens. No warnings, no messages from UE. This week all was fine, but 2 days i have this problem. I add only materials, not new meshes or lights or something, and in some point this situation happened. For some reason i reloaded two meshes, but i dont think this can be big problem for UE.
Project - nothing special, office openspace with basic materials. Did anybody have same problem? What could be reason of this problem - some incorrect material, or this situation proves that my PC cant handle project?

Thank you in advance.