When using the default sphere scene stopping the render takes only a few seconds (before the “render” text turns blue again) – seems normal to me. Closing Bella after that happens without delay.
Denoiser is on, but diffraction is not enabled. Render resolution is my perspective viewport resolution (4224 x 2624).
Saving directly to the hard drive – not over the network.
With force stopping the render stops and I can close Bella without the delay – even if the “render” button doesn’t turn blue again (delay there compared to the default scene) before closing Bella.
If I’m stopping the render the normal way and then closing Bella, I get the long delay (not always 5 min, though).