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This sounds like the table is applying an extra paragraph formatting rule on top of your Norm style.
I’d check the table style itself first. Click inside the table, go to Table Design > Table Styles, and check/modify the table style’s paragraph formatting. Also select one of the affected paragraphs and check Paragraph > Spacing > Before to see if the 6 pt is being applied directly.
The fact that Word shows Norm + 6 pt before makes me think the 6 pt is coming from table formatting or direct formatting rather than the Norm style itself.
If it only started after a recent Microsoft 365 update, I’d also test the same table in a new blank document. That could help determine whether it’s a document/template issue or a newer Word behavior.