Question Interference on external monitor display ?

Jul 20, 2022
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Hello All,

On an external NEC VGA monitor connected to an Air running Big Sur via the Thunderbolt / USB-C port. Official Apple adaptor afaik

It is intermittent and only occurs on the external monitor, not on the laptop screen.
Thought it may be the cable but replaced with the same results. Could overheating cause it?

Thoughts please!
Thanks

(I was going to post an image but can't find an option to upload one..)
 

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