Excel & Word changing permissions when saving on an Apple iMac

[HampshireELM]

I raised this months ago on a Microsoft forum yet I have no solution. More and more people are saying they have the same issue.

I use an iMac (there's no server involved, it's a simple system) which I share with my husband and we have a number of files which we share maintenance of so we both have read & write permission on these (as individual users). Annoyingly, when either of us use Microsoft Excel or Word for Mac and save a file, the file then only has read & write permission for the person who changed it and the permission for the other user disappears completely. 

I've tried setting up a group with us both in it and giving this read & write permission too but this permission disappears when I change & save the file.

I've also tried setting up new users and the same issue happens with them too.

I'm using the latest versions of both Microsoft Office (16.27) and Mac OS (10.14.6) and have an Office 365 subscription. Despite upgrades of both systems since I reported the issue, the issue still remains.

I don't have the same problem if I use Apple's applications but I prefer Microsoft Office.

Why is this happening? When will there be a fix for this?

[#2]

@HampshireELM 

I have the same problem with one of my customers.  They have a share downstairs on a mac mini and two of the employees have access to the files in the share.

Every time one opens and saves a file the other can only open the file as read only, even though if you look at the permissions the user is on the list listed as read/write.

I have read that this also has to do with Apple's sandboxing methods as well.  Not sure but I wish they would fix this.  I get a call at least 3 times a day to remote in and fix the issue.

Come on Microsoft seriously this is expensive software to be having such stupid issues with.