Strange artifacts that come and go on images.

If there are any shiny surfaces inside your imaging train, a bright star slightly outside the field of view can produce a reflection.  I have had such reflections in the past with both a C8 and a C11 EdgeHD, but in both cases, they were thin and strongly curved.   Your reflections are much wider, more diffuse, and irregularly shaped.  I wonder if it is an external light source (e.g., neighbor's spotlight) reflecting off the inside of your dew shield?

@Michael Ring I haven't tried rotating yet, I'll try that tonight if I see them again.  

For the puzzling images, they're cropped from a screenshot of the original raws.

@Joostie I'll put more tape on any seams I can find.  I tested this theory with a flash light and didn't see any light spilling in when I shined the light around the image train.  But one morning I wanted to image the sun with this image train, and tons of sunlight was pouring into the train and made weird patterns, so it might just be the seams and joints need to be sealed.

Edit:. Yes I used a white light filter😆

I have the same setup, except no OAG, with a C925. Can't say I have seen anything like it.

First color is red, so the source is red. The red streaks from M1 could be some sort of reflection of M1, or something on the optics in the image train that is really dirty/wet or oily, scattering light in all directions. It is really suspicious that two rays seem to originate at M1 and they are red like M1 (the sky is typically a little green in a raw image, so the green from M1 won't be so obvious in a reflection). And the other red ray is parallel to one of the rays from M1. But awfully strong reflection/scattering to do that. Do the two reflections follow M1 if you move M1 in the FOV? Better yet, get a really bright star in the FOV and see if you get an even stronger reflection/scattering from that. If it is something on the optics, rotate you camera and see if it rotates with the camera (it is on the sensor) or not (it is in the telescope optics). 

It could be external light–if so that light source is red since you are seeing red streaks–could it be a red LED from a power bar, etc?. Do a dark with the lens cap on in a dark place and then do one with light around the telescope. If there is light leaking in it will show in the dark when there is light around compared to the dark with the telescope totally in the dark. If there is no difference then there is no light leak. If there is stray light in your dark with lights on, you do have a stray light issue. In that case, run some darks again in the dark, but take a flashlight and for each dark shine it on a different place on your telescope–this way you can see where the light is coming in and isolate the problem very quickly. If it is a leak my guess is the OAG, as hard to see how light would get in the train anywhere else typically–you don't mention if you have a filter wheel or drawer, another possible problem for light leaks.

Good luck
Rick

@Rick Veregin I don't have a filter wheel.  This is a new issue for me, and I think it started happening since I started using shim spacers.  I already put tape on one seam/joint, I'll have to do the rest of the train.  Instead of 5min exposures with the flashlight as you suggested, I could do a live 3 second loop with a bright LED flashlight.  As I've stated there are no light sources nearby that could be causing this, I've made sure to put the rig in the darkest corner of my yard, where my garage and fence meet.  The only light source near the train is the red power LED of the motor focuser, but that light is pointing down, is recessed, and not very bright at all.

I think I nailed it.  Covered the entire image train from visual back to the camera's vents with a towel.  No more light leakage.  I know this isn't a solution to the original issue but at least I can mitigate it.  

Congrats on solving the issue. It was a perfect who-s-done it :-)

Glad you solved this one.  I had some reflection problems (for the first time) with my rig, and a blackening of the inside threads of my assortment of spacer shims did the trick.

@Ian Dixon My spacers are a little shiny, and I could give them a matte black finish, but it is much easier to just get a black towel and cover the train.  I'm wondering if/how this will affect temps inside the train.

What is the ambient temps you normally shoot at?  Perhaps the towel is the way to go... simplicity is wonderful too.