What is occurring when a workbook shows "Preparing worksheet" in the status bar? 

I have a workbook with several Power Query connections to MS Dynamics CRM spreadsheets. Three of the connections are loaded to the Power Pivot Data Model. The loaded tables are not large -- two with 3,000 records and one with 82 records.

I find that the workbook frequently freezes with the status bar showing a progressive Preparing Worksheet bar at the bottom, followed by auto-recalculating the worksheets. Some of this I understand when changes to the Data Model call for refreshing related tables in the workbook. However, it often goes into Preparing Worksheet mode simply by switching views back and forth from the workbook to the Data Mode. The challenge is that each time this brings work to a standstill until the process completes.

Short of putting the entire workbook into Manual Calculation mode, is there any way to minimize this activity? It's causing long delays while waiting for Excel to catch up.

Thanks for any suggestions.

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Excel 2016 64 bit
Windows 10