Those look like process errors. And I think this is a conceptual error:
My operating theory up til now has basically been that the unaided human brain (or at least my unaided human brain) can’t avoid errors like these.
And I think there are conceptual errors related to processes/methods. Those don’t look particularly related to conceptual errors in “math” (e.g. the stuff they try to teach in math classes), but they are relevant to doing math well.
One way to approach process errors is by trying different processes and monitoring for changes in error rate, types of errors, etc.
For example, it looks like sign errors are a common category of error generally and for you. If you wrote all negative signs in a different color which stands out, you might make fewer sign errors.
I haven’t tried them, but a quick web search indicates that many erasable colored pencils are available.
Other ways to vary process include using apps (there are many types, like free drawing, vector art, whiteboard, visual apps meant specifically for doing math work, regular text editor, math-oriented text-based app, etc.) and input devices (e.g. mouse, keyboard, stylus).
Another process variation would be to use pen instead of pencil. Or to use graph paper and consistently write one character per box (one result is minus signs would get a whole box to themselves). Many others could be brainstormed and then tested for advantages and disadvantages.
A different sort of process change is to go through math steps more explicitly and write more out.
A different sort of process change, which is harder to test, is paying more attention to detail. It requires a sort of mindset change. Finding a way to pay a lot of attention to detail, and to actually somewhat enjoy it, is important to doing math well. It’s kind of similar to the attention to detail needed to read and write accurately in discussions. Coding in languages with complex syntax is another thing that requires attention to detail (dealing with lots of nesting also requires attention to detail). Dealing with shortcuts can also require a sort of attention to detail, because you have to accurately track more stuff in your head to make up for the skipped stuff. With writing, sometimes when people write less stuff and make it sloppy and don’t explain some parts, that requires more attention to detail to read, despite it being imprecise. That may be counter-intuitive. But if the author gives less information, then the reader has less information to go on, which means he needs to squeeze more value out of the information available – and getting more out of a given information is a type of paying more attention to detail.
Another process change is going more slowly and carefully. Can you actually stop making all these errors if you go slowly enough? What about with no backtracking or double checking, just being more methodical?
Another process change is doing different types of practice when learning skills.
Some errors may be related to doing exploration during solving, rather than knowing the whole path to the solution from the start. In that case, one of the fixes is to consciously know, and perhaps label (e.g. different color writing) which stuff is exploration and which are a final, organized solution. One way people make a mess is they do something that might work, but they aren’t sure if it’ll work. So it’s exploration. But if it does work, then they recharacterize it as non-exploration and continue instead of redoing that part. This is similar to, when coding, writing a first draft of a function to try out an idea, and then finding out it produces the correct answer so you just call it done with no refactoring, no step where you consider how it should be organized now that you’ve got the (this part of) the solution worked out.
Broadly, fixing one type of error helps find other types. Sometimes people think “I could do X to fix this; it’s just not worth the effort.” They may be right. But they may not. If they actually did X, they might find the error still isn’t fixed. Why? Besides them being just plain wrong, they might have had two or more problems. They knew what was going on with the most visible problem, but it obscured another problem. If you fix these sorts of arithmetic errors, you’ll either do much better at math or find that it’s now easier to do problem solving for remaining issues because then there are fewer factors involved.