Hi Aldo,
I asked around in the dev team. We did not change the save logic of a workflow in quite some time. We also had a look at the code again, and cannot see anything obvious like accidentally trying to access a path with trailing slash as a file.
Also, there are no internal tickets that sound related and try to fix a “Access is denied” problem – for neither of the versions you mentioned. I looked over all 47 closed tickets for 5.3.1 and neither of them had something to do with the code in question. Therefore, we cannot think of a reason related to Analytics Platform why it would suddenly work on local drives in 5.3.1. It must be some permission problem or something with the Windows setup you are using.
But, I found some related problem in the forum: Unable to save_as workflow due to File access problems Math Formula node (Access is denied)
A helpful link to Microsoft suggested that the # character might be forbidden in some organizations’ OneDrive or SharePoint setup: Restrictions and limitations in OneDrive and SharePoint - Microsoft Support
Some organizations don’t yet support # and % in names. If you’re a global admin or SharePoint admin in Microsoft 365, see Enabling # and % Support on the SharePoint blog to learn how to allow these characters.
To diagnose this a bit further, you can put a test file containing the # character in the filename into the workflow’s data directory, e.g. C:\localK\w5\XXXXX\dev\0100E\XXX_k5_43\data\testfile #123.csv, and read it with a file reader node and write to it with a file writer node. It may also help to put that test into a loop with a wait node so it is executed periodically. This may be needed because you wrote that the problem happens “after a while (minutes)”.
Regarding node resetting:
The file is not absent if all nodes are reset. It is always present if a workflow is saved normally (“Save” or “Save As”). It is only absent if it is exported without data (link to source). So the particular file should not be the problem.
Best,
Manuel