Thank you for your posts and please sorry for the delay in our responses.
As for progress in solving this issue, we continue looking for a way to solve this.
Regarding a reason for this, this is caused by internal processes launched by Visual Studio when saving a file. We found a similar discussion here. The issue is reproduced as for VS 2017, as well for 2013. Since The Welkin Suite for Windows is based on the Visual Studio Isolated Shell 2013, some of the issues which are present there can appear in TWS.
One one hand, we are looking for a way to find an exact reason for this behavior or some regularity for reproducing the issue, on another hand we keep our eye on updates and bits of advice from the Visual Studio team on this issue.
Meantime, we can see that the files with the different extensions, like *.loj, *.v04, *.3c3, etc., are temporary backup files which IsoShell creates when saving a file(s). You can delete them and check if the issue is reproduced.
As for the message, that a file is used by another process, we have been faced with one additional case of appearing this message when a project was created on some external storage, for example, OneDrive, Google Drive, Dropbox, etc.
Can you please let us know if your project is created locally or on some of such storages?
If you use any external storage for your TWS project, I kindly ask you to create a project locally and please check if the issue is reproduced.
Also, if you don't mind me asking, can you please check if the issue is reproduced when you wait several seconds after editing a file (5-7 seconds) and then save an edited file.
We continue to investigate this issue and will do our best to find a solution for this as soon as possible.
Thank you for your collaboration.