Unable to save file (Well... Sometimes)

[Bluetube]

I have a workbook that is saved as binary .xlsb that we (three people) use on a daily basis. Starting around January of this year, about once a week after one of us would open it and select save, we?d receive an error message stating the file is corrupt and can?t be saved.
We managed to find a work-around, if one of us that did not receive the error message open, save the workbook and then close it. Then the person who received the error before can now save the workbook without any issues. Then there aren?t any issues again until usually about a week later.
Over the past two weeks this work-around has been less effective. For instance, this week all three of us were unsuccessful at saving the file.
But for example, if I reached out to someone else (not one of us three) and requested them to open and save the file. Then we are able to save the file again as well.
Even stranger, today I had someone outside our group open and save it. I went in and still could not save it. Then, I asked a different person outside our group to open and save it and then I was able to do the same again, as well as the rest of my team.

Unsuccessful Solutions Tried:
Opened Excel in Safe Mode and did a file repair.
I ensured the three of us had the latest Office updates.
Tried to save the file to my local drive.
Opened Excel changed calculations to manual and then opened the workbook.
Tried changing the suffix from xlsb to xlsm (since it does contain macros).
Posed the question on MS Office Tech Community a month ago but never received a response. (I deleted the post today to prevent cross-posting)
One thing I did notice is when this occurs I am unable to view any of the macros in the workbook. When I select VBA and double click on any of the macros nothing happens. When I select Reference, Tools nothing as well.
I have researched the heck out of this and have not been able to find a solution.

I can't share the workbook because it has sensitive info and it would take me forever to remove all of it. Plus if removing it fixed the issue I would not find the error.

There has never been a corrupt Excel file I have not been able to open or fix. While this one we are able to still find a way to utilize it, I am concerned that we might not be able to one day. This file would take way too long to rebuild. I do not believe this file is corrupt but can?t figure out what may be causing the issue.