NEED ADVICE re serious issues on collaborative company workbook. Appealing to Reddit's Excel wizards as a last resort.

I work as part of a small team sharing an Excel workbook with my associates. The document is integral to company operations and requires continuous updating on multiple fronts. It is very large (7MB) and extremely complex, with about a dozen sheets using complex, interrelated formulas. There are up to four people on the document at any one time, with two of them making constant edits and using heavy filters throughout the day and the other two primarily just filtering for key items to inform business decisions. All four usually operate from different locations, sometimes across the country. We recently expanded the operations team from one to two people, since which time the document has been experiencing significant issues—none of which occurred prior to the new associate joining. These issues appear to stem from the new situation of having two people editing simultaneously for the first time, and include:

• Merging problems
• Regular crashes
• Filtering issues, such as when we are both filtered within the document and one person uses control+D to fill down in a filtered column, other rows that the one person’s filters do NOT show in that moment have been filled in as well.

The workbook is stored on OneDrive but accessed and edited through the desktop Excel application with AutoSave enabled. Surely we are not the first business to face this issue. Are there any solutions we may be overlooking? How have other businesses approached such matters? It is imperative that the workbook remain updated in real-time for all involved for business purposes. Finally, please let me know if any other subreddits or communities (perhaps discord?) come to mind where I may find answers to the above.