I noticed a strange mesh effect in the sky (as in the attached image). It seems to happen whenever the phatom is recording against light, mostly on the sky.
Any idea what might be causing this problem? It never happened before, but seems to be a constant problem now.

Do you have overexposure warning enabled?

Yep - that looks like a version of the zebra lines (over exposure warning) which is set in the app. Ensure this is turned off. Failing that this looks like a sensor/hardware issue which may need to be returned to DJI but I may be wrong.

It is not the zebra lines for over-exposure, they are heavier and at a 45 degree angle. That is a faulty camera.

https://forum.dji.com/thread-28526-1-1.html
this thread might help

Hey there, does the issue only appears in live video? How about the original pictures in the SD card? Please help us confirm, thanks!

Unfortunately, this is not the overexposure warning, since that's turned off.
The issue appears on the video taken from the SD card.