Thanks for your answer! Yes, actually this was the case. I have eventually also noticed this and recreated a much smaller canvas. I will proportionally upscale it when it comes to print preparation.

Just to be sure, Zsuzsanna, — are you sure you are not in the Large Canvas mode? To check this, try to create an artboard larger than 6000 mm — if Ai allows this, you have a document with an internal scaling coefficient (Ai warns about it with a ⚠️ when a document like this is created, but not alter).
Brushes are known to misbehave with the mode, as reported here: http://illustrator.uservoice.com/forums/601447/suggestions/41713246
Also, please attach a test document with both brushes used.

When drawing with a calligraphic brush in Adobe Illustrator (latest version via Creative Cloud on Windows), with Wacom Cintiq, the stroke appears visually offset by several pixels from the actual path.

In Wireframe view, the path is in the correct position, but in normal preview mode the rendered stroke is shifted.

Interestingly, if I switch to a different brush (e.g. a basic non-calligraphic brush) and then switch back to the original calligraphic brush, the rendering corrects itself and the stroke aligns properly again.

The issue seems to be document-specific: when I create a completely new document, the problem does not occur there.

System info:

OS: Windows
App: Adobe Illustrator (latest version via Creative Cloud)
GPU: NVIDIA GeForce RTX 3060 Ti
Screen/Pen: Wacom Cintiq

Notes:
This appears to be a rendering issue only, as the underlying path remains correct in Wireframe view.

I have a stroke with a simple art brush, and when copying it into a large document (the target document is 7x7 meters), the actual artwork is offset from the path. If I decrease the size, the art moves towards the path, and inversely, if I increase the size it moves away from it. Copying the path into a new, smaller document does not have this issue.

Also, expanding the stroke/brush in the large document, results in the graphics being expanded where it is shown - not where the actual path is.

I have also noticed another bug relating to large documents, that when pasting artwork, it ends up far away from the center of what is in view, where objects normaly show up when pasting. But some graphics get pasted way outside the artboard (and no, I am not using paste in front/behind).

It is impossible to make an illustration with this bug. I use a large canvas and Wacom Cintiq Pro. Have the same problem as described above.

Adobe will never ever get interest in any bug ... they simply do not care about it.
It does not only deal with strokes only. Everything you copy / paste will get an offset. Such a shame this issue is back from 2020!

The offset is caused to any object like rectangles or grid lines, too ...

A similar problem, but with mesh envelope distortions:
http://illustrator.uservoice.com/forums/601447/suggestions/49773365

Just updated Illustrator to 29.2.1 and still having the same issue. Brushes are generating offset from the path and at the incorrect scale.

I encountered this issue as well in large format document adobe illustrator. It seems to offset more or less depending on the type of stroke I make also. Very disruptive for detailed brush work.

me too!

Still happening on large size documents in 28.6.

Still wrong on 28.2

Still happening in 28.0

Still having this error on an oversized artboard using charcoal brushes 5/26/2023

Here is my working environment.
Illustrator 27.3.1

iMac (latest OS)
3.6 GHz 10-core Intel Core i9
AMD Radeon Pro 5700 XT 16 GB
128 GB 2667 MHz DDR4

Copy and paste to normal canvas will fix the misalignment.
Copy and paste the corrected path to the larger canvas and the misalignment will be restored.

This happens with large document sizes.
Please see the screen capture video I recorded.
I hope it will be resolved.

This happens with large document sizes.

However, I can’t confirm this problem to not exist in versions prior to 2023.
26.5.2 shows the same behaviour.

Upon investigation, I see that the brush you are using is a giant path, 98.0938 inches long and 5.3154 inches tall, in the document’s units.

However, the scale option chosen for the art brush is 'Stretch to Fit Stroke Length'. So it means that Illustrator should maintain the 5.3154 height of it (that it a width or 'weight' of the stroke) across the line, which is not the case nor in 2022, neither in 2023 versions!

If we rebuild the same giant brush in an much older version, such as CS6, Illustrator maintains the original height of the artwork used — as intended.
So it’s not 2023 got broken, but 2022 before it!

This needs further investigation.
Meanwhile — what was the latest version you say you were able to use this specific 'fat brush' succefully? Are you sure in that? It can’t be 2022.

DG, thanks for the file.
I confirm this issue.