Excel is waiting for another application to complete an OLE Action . . . No it isn't . . . Or is it

Kit: Surface Laptop 4, Windows 10, Excel 365 (No Add-Ins are enabled, "Ignore other applications that use DDE" is ticked).

Storage location: Local, Network shares both NetApp and Windows.

I've created a blank excel file (no links, formulas or macros), and populated millions of cells with the word "Testing" to create a simple file (test.xlsx) that is 50MB.

Stored locally on the C:\ Drive - it opens fine. Stored on a network drive, I need to click OK to "Excel is waiting for another application to complete an OLE Action" several times before it eventually downloads and opens.

I understand it takes longer top open a file from the network, but what is this message for and what is it really waiting for? The file only contains cells with the word "testing". If I delete some cells to make the file smaller, eventually it doesn't happen. It's just something that happens when the file is saved on the network and is over a certain size.

The problem is that users often click "OK" a couple of times, then click "CANCEL", assuming the file is corrupt or broken - and then get angry.  Telling users to sit there constantly clicking "OK" until the file eventually opens is surely not the way forward. Can this message be suppressed perhaps?