First - I've been doing this for a long time... Published in over 30 countries on 6 continents in just the last year with another stock house. The past 20 years have similar stats. I don't say that to brag, but to tell you my experience level. I currently shoot with a pair of Canon 1DMKIV's and a wide assortment of Canon "L" lenses. The bodies will soon be 3 generations old, but they are still pretty awesome units and the glass top notch. The sensors and glass are cleaned regularly. There is no motion blur in the image. No trademark or copyright infringement issues and the items I shoot don't require releases. All are submitted to the creative side... Snow storms and things that effect the agricultural industry around here aren't considered editorial for some reason, but that's another issue.
So, on to the issue. I live in the Midwest USA. Corn and bean country and the land of (this year) early snow storms. In the past week, I've shot and submitted images from the dusty harvest of the plains and the snow storms of early winter. My images get processed by the subscription model of Photoshop... It's up to date with the last release of a week or so ago. The images shot in the elements have spots as you can imagine... dust in the air from the discharge chute of the combine and the dirt from the wheels and engine fans, and snow falling from the sky. I blow up the images to full size and pan through them and can find not one thing I'm not proud of, yet boom - DENIED - TECHNICAL ISSUE. Not one clue of what the technical issue is. Just a stamp of disapproval and I can find no way of appealing or even inquiring as to what they are or aren't seeing. Not even a place to explain in the submission all that I've just typed here.
Frustrating.... It's been that way for the past year or so that I've attempted to place images here. Is this normal? My acceptance rate is absolutely degrading.
[Moderator added the Contributor Critique flag]
As I read, you are very experienced in photography and with stock images. Neither your camera nor the described subjects are the problem. However without an example it is difficult to see what the real problem is. All I can do is to point out to the rejection reasons: https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html.
But as you are that experienced I suppose you have read that all.
I suggest you post a rejected example file here so that we could eventually advise. Unfortueately the new fora are a mess as they do not allow full resolution images to be posted. I suggest you use a CC link for that.
Technical Issues is an overall reason that points out issues in composition, contrast and saturation in your image, as well as white balance.
In particular (From Adobe):
Image Quality (used to be named 'Technical Issues")
If we determine your file to have technical issues other than focus, exposure, or artifacts, which we call out specifically or if the file is determined to not meet our overall quality standards the "Image Quality" rejection reason is selected by moderation.
Photography and video technical issues include but aren’t limited to
White balance: The white balance may be too warm or too cool.
When you shoot in raw formats, you have great flexibility to adjust the white balance in your post-processing workflows.
Contrast: There may be too much or not enough contrast.
Saturation: Oversaturation may give your file an unnatural look, but under-saturated or spot color can also result in technical decline.
You may want to try the Vibrance slider instead of Saturation in Lightroom.
Selections: Editing must be done inconspicuously. Selecting objects out of their backgrounds (or masking) to composite into new images requires time, patience, and care. Do not submit images that have been poorly selected or look like they are not a natural part of the scene.
Chromatic aberration: Refers to color fringing around objects in the image.
General composition: Is your horizon straight? Have you cropped the image too much? Consider leaving a designer room to add their own text or objects.
So, as suggested, post and an example and we can try to point out what type of issues could cause a problem.
Both me and Abambo are contributors, so we are very familiar with Adobe's rejection reasons.