Path Traced rendering "flashing" problems

I am starting to render the first shots of my 50 sec clip, here is the first test:

Native Sphere lights are causing these flashes, if you watch closely. That was rendered with 128 samples. motion blur samples 5. I tried it with 256 samples, but no help:

What can this be, please help.
Here is the “flattened” version of my simple scene:

I’ll be sending this to the dev team now, thank you for bringing this to our attention.

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I thought I had found a solution, but it turns out that the changes I was making which seemed to solve the problem made it appear in other parts of the sequence. I’ve been told it may involve a known problem with the version you have that has been fixed in the next version. I’m awaiting more feedback to see if there’s a recommended method of mitigating the issue in the version you have.

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There is no sure remedy for this issue in the current release, though it’s fixed in the soon-to-be-released next version. My suggestion for now would be to experiment with different direct light types and even dome lights rather than the large radius sphere lights. Also, for this scene 128 samples is probably excessive. You might try with fewer path tracing samples and more motion blur samples.

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Using disk lights solved the flashing light issue,