@reddeercity, but half-frozen preview would be a good way to see what you are filming without any delay in 48fps.
I Think there maybe a issue with your battery grip (dirty contact etc. ...)
Will try to clean the contacts, maybe it's an issue, but not sure, because anyway, the camera behaves badly. And yes, i have original canon batteries.
They do burn out from time to time , FYI I don't restore my card in cam (Format in camera & replace ML build) unless there's a good reason too
I will be more careful and follow your advice to don't format it without the reason to actually do it to save NAND's life

Thanks for the link.
And good news for me. The Lexar card started to work again as if nothing had happened... What is it? I don't really know. The interesting thing is i low level formatted it with Hard Disk Low Level Format Tool, the format was done successfully (but anyway it still wouldn't open, the same process i done with the 1st lexar), but all the files are still there on the card... And i can format it now.
And i'm sorry for disturbing and waste your time. Don't sure i wrote in right threat.
Also need to say that bought the camera like it was a new one, but later noticed some bugs:
1. Magnify jumping out to 3x3 automatically after randomly count of seconds
2. The sensor was "covered" with a lot of artifacts and strange patterns. All of these disappeared after i cleaned it with a special swab.
3. The serial number on EXIF metadata was different from the serial on the camera body. And i ever read the name of the previous owner.
Of course, i bought it for the price like it was new. In the store, they told me that they didn't know about it, and also told that if i had any problem they repair the camera by themselves...
That time i needed the camera so much, because my 650d's sensor deteriorated after a trip, so i decided to leave the cam with me.
It was a kind of wrong way =)
Now i thing those bugs appear with the new force (all this i write because is started to appear with Exp. build and including because maybe it could be a kind of useful for the development):
Mirror doesn't go up and the camera doesn't switch on (with magic lanter uninstalled). After several (regularly 3-4 tryings) it starts to work. But step by step... look:
pressing trash button because of the habbit

Also, sometimes i have color changing on video or more frequently on photos (especially first 20-60 seconds when i activate preview)
Look, this photoshoot i did three days ago. (i cant show the model here on this forum including because it's a nude photo)
one photo has this color:

And after several times it has "normal" colors:

But from time to time the color changes slightly thats why i wrote "normal" (i newer use AWB)
Also, there are vertical stripes sometimes:

Sometimes i got a mix of it's all.

Another thing...
After this photoshoot, i notices a strange texture, zoomed it, and was slightly shocked.
Just look a that




I have no idea what it is.
That was a non-commercial shooting

This all are so strange and started to appear after i installed experimental build the 1st time, but i think it's only coincidence, or maybe this story will be useful for development of this experimental build
For my work, i decided to rent another cam for now

, and don't know what to do with imy one. Maybe i need to bring it to any repair service, but I am not sure they understand all of this.
or buy a "new" used 5dii when have enough for it.
But while i'm thinking i'd like to share some files CRASH00.log and log000.log (not on lexar card, but after it stopped to work iinserted another one (sandisk extreme) and saw some crash log files). I don't know if it can be usefulm but anyway...
https://drive.google.com/file/d/1N5gaSjCsRfeDB9eJgfI9LEc4Ci0TKKB6/view?usp=sharinghttps://drive.google.com/file/d/1K1K6mvRW6O2mhQOTDGgZXkrb1b0Cxpe_/view?usp=sharing