What did happen here? vol.2

[alexvaras]

And now with the Contax IIa.

We had some activities in the school on Friday and I had a roll loaded on the camera that I finished outside, all ok, I loaded a color Fuji C200 I had at home and 4 first frames were ok:

At fifth this started to happen:

This big and lower lines started to move a bit up and down but mainly in the upper part of the photo.
About 25 photos have this but when I can inside the building the line disappeared:

I finished the roll inside, should I check anything on the camera? As I said the previous BW film went ok.

Mike or anyone with Contax and collapsible lenses, could it happened I didn't opened correctly the Sonnar collapsible? I say this because probably I closed the lens going inside the building the opening back again inside.
The film was processed on a lab.

Thank you in advance,
Alex

[Julio1fer]

Looks like a light leak to me. In the negs, does it go between frames?

I have a Contax III with collapsible Sonnar. If you do not open the lens correctly you get out of focus, but not light leaks with this pattern. The lens seems an unlikely cause.

The horizontal pattern could be caused by a shutter issue. Maybe when the shutter got to low temperature it acted out?

I am assuming that you can verify the issue in the negs, to discard a scanning problem.

[alexvaras]

Sometimes it the line ends a bit further the frames, sometimes it crosses from frame to frame or they join together from both frames.
Here example:

As well you can see how abruptly end when the next photo is inside.
About the shutter cold, I don't think so, the Contax was already in my backpack at least 20 minutes when I was outside, I took it out and finished about 15 photos from the BW film I had, no lines at all. Only after 4 frames with the Color Fuji film I noticed this and when I went inside I continued doing photos, maybe it was 5-10 minutes after getting inside.
It seems indeed a light leak, but then why it didn't show up inside the building for at least 8 frames?
More theories?:)