Strange glitches in Vray 5 2.3

[Blakk76]

Hello,
out of the blue V-ray became unusable because of the strange artefacts during render.
In CPU mode reflection is flickering every single frame and in GPU mode strange "bad blocks" are appearing during render (see attachment)
Nothing was changed in the system, drivers etc and this problem appearing in every scene

[vladimir_krastev]

Hi thanks for posting. This is indeed a strange issue the way you describe it. Could you upload the scene and assets from the example above for review? If you do not want to do this publicly you can use the support contact form where your files are kept confidential.
Please share a bit more details about your setup, are you using network or distributed rendering?

[^Lele^]

These look like adaptive lights artifacts.
You can change the options in the render settings (use "full evaluation", see attached screenshot.)
See if this helps, if not, do as Vladimir suggested and kindly pack us one of the scenes for inspection.