Melankolia flickering like a dying fluorescent lamp, why?

[JPB]

As title. All other themes are smooth as yoghurt through a dog, but Melankolia has a leafy patterned border to either side of the central portion and these areas flicker like the flickeriest (OK, so I got a red line for that one but..) thing you ever saw.
This happens when I'm running on battery as well as on mains and in any case, sound is unaffected.
I love the idea of the theme because white text is so much easier to see, but why do the borders do that, Terry?

Rich, have you been using a JCB at the edges of my monitors?

[rich.]

im sorry everybody, ive broken johns internets

[JPB]

im sorry everybody, ive broken johns internets

Well ah'll be an uncle's monkey, it's fine this morning, perfectly stable, no flickering and I can see every detail of the patterns even when I send the page directly to the bottom.
Could it be that my room lighting, because its refresh rate is slower than that of the screen, created some form of magicks?

Sorry Rich, daylight was to blame because it went away and made me put the house lights up!

Hang on though, what's this.. EXTREME purple and red? Nice, and teeny weeny margins so they look stunning on a 21:9 display.
Nice work Terry, great colours and white-on-black text FTW! All that's missing now is a bright orange environment to play with!