White balance changing while recording

[Pe11e]

Hi!

This is my first post here. I bought D5100 few days ago, and already fell in love with it. After D40 and D3100, this is my third dSLR, and first that is not pure entry level camera. Anyway I'm using custom firmware to unlock manual control in M mode when filming (manual ISO, shutter and aperture), and I noticed a very strange issue with white balance while filming. Few of steady shots from a tripod are cold at the start and gradually changing white balance to warm in few seconds time. I'm always filming with WB Auto since I never noticed the issue with D3100, white balance never was changing during recording. Is this some kind of D5100 bug, possible "feature" when WB is on Auto, or I must lock AE before recording? When in M mode, AE is locked because ISO, aperture and shutter is controlled manualy, so that's why I'm never locking AE via button. So I guess I must choose WB preset before each shot, maybe it will solve the problem? Strange thing that D3100 with manual movie mode control never had that issue.

Your experiences?

Cheers and thank you in advance!

 

[Needa]

Have you posed the question to the people who created the custom firmware?

 

[Pe11e]

I didn't, wanted to see if this has any connection to WB itself, or AE lock, with custom or default firmware. I certainly will post the same question if no one can confirm this issue here.

EDIT:

Here is the sample of the issue:

You can spot the difference in WB just by looking at the walls or sky.