I would use a Caption style for the table caption but otherwise add a below spacing to the heading style that you are using as a caption.
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Table styles are very tricky beasts, they are not true styles but macros that trigger on changes. I recommend not to use table styles unless you use them in a very limited way and know precisely the how they work.
Once a table style has been applied to a table you cannot remove it, only change it to another table style.
To Remove a table style
- Select the table and click Table > Convert > Table to Text
- In the dialogue make sure Tabs is selected under* Separate Text at
- Select all the text that belongs in the table and click Table > Convert > Text to Table
- In the dialogue, under Format, make sure that None is selected