Dual-iso corrupted frames on 60D and 550D

[gcrook]

Lately ive started using dual iso to shoot raw (camera CR2) timelapse sequences.It generally works very well but very often i get corrupted frames on both my 550d and 60d.
It could be any number of frames from 1 random frame to tens or hundreds of pictures in a row or in an unspecified order.
All these frames appear to have a colored or black or white block overlayed to the photo usually in the right corner im my 60D.In my 550d they look like white purple interlaced blocks.
Sometimes some bright areas like clouds look like they have clipped to purple color.
I have been using various modes to shoot timelapses it has happened in both manual and av mode and i have no idea how to reproduce it.
Will it help if i upload some raw files but before that does anyone have the slightest idea why that happens?

Edit:Pardon me the CR2 raw files seem to be fine.These artifacts appear only on the converted dng pictures using cr2hdr to extract the raw files.Needless to say ive used a lot of nightly builds so maybe the problem is in the conversion?

Examples, just this morning from my 60D.Dual iso 100-800.

http://postimg.org/image/4n4adx07r/
http://postimg.org/image/5vrxe0qi7/
http://postimg.org/image/4cu3rhmxn/  ----- This one is new never seen this kind of image degradation before.

[a1ex]

The block looks like corrupted data in the CR2; try with another card.

The last one was not converted; did you get a DNG for it? if yes, upload the CR2.

[gcrook]

The last one was actually converted as well,all these files i uploaded were converted from the -converted- dng's.
Dont think its a card issue since this has been happening with every card i own (4-5 different sandisk 32gb 45mbps cards).All the cr2's appear normal i double checked but unfortunately i deleted them all this morning sorry about that.

P.S Dont know if that helps but now that i think about it this usually -but not exclusively- happens in cases where i do a day to night timelapse with auto shutter
and as sky darkens foe example, shutter exposure gets close to intervalometer interval, thus forcing the camera to expose immediately for the next picture without time for liveview to show.I had a case where i got no less that 120 "blocky' frames in a row and as soon as night came and i changed to manual all frames were normal again.Maybe its coincidential.Another case where it may happen is where i do a manual mode timelapse and i half press the shutter between intervals to note down the shutter value.Again ive spotted this a few times because i remembered that i did this during the first 5 frames and one or two were corrupted but not really sure (silent pics was not enabled btw).Do all these mean anything?I have no idea to be honest.

edit:Just finished importing and checking a new batch of timelapse sequences i did a few hours ago.Same camera (60D) ,lens, and card.Changed nothing in camera as far as settings,modules etc.Did various combinations of 100/400 and 100-800 dualiso but all of them in manual mode this time and not AV.Not a single corrupted frame in no less that 1000 raw pictures....

[gcrook]

So no idea as to why this occurs?Is it my fault?Am i the only one getting these images?

[Audionut]

You should find a way to reproduce the error, and upload a CR2.

[gcrook]

You should find a way to reproduce the error, and upload a CR2.

Ok audionut i'll shoot some tests and report back when i have something.
Any ideas btw where i could upload a few files?Dont have a cloud service.

[ansius]

wetransfer for example and many cloud services have free limited spaces, like dropbox, google drive, etc.