QB Issue Resolution:

Snap Shot is the same as having any other report open, any activity in QB refreshes the report. You can try resorting all lists and running file>utilities>verify and rebuild data to see if that helps but expect a hit in performance with Snap Shot left open.

Resolution for Issue 'Why is Quickbooks for Mac suddenly running so slow?' available: Yes (Solved).
Source: Intuit Community forum.

Why is Quickbooks for Mac suddenly running so slow?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

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