This behavior usually occurs when switching fast between render states. Because V-Ray NeUI waits for the host app to tell it when the renderer is done, starting and stopping a render process rather quick can cause discrepancies in reporting render states.
We could only suggest to be a bit more patient when a render process is initiated or ceased.
The issue might be more evident in some projects due to their complexity.
When initiating a render job, the bootstrap phase will vary (time-wise) based on the assets and all other information related to the project. In that respect, for example, if during the bootstrap phase the process is stopped and started immediately or shortly after, the issue could occur because SketchUp cannot report correctly the fast change in render states.