Browser repaint caused by patterns and other Javascript DOM modifications

I am currently using Plone patterns for the first time (and perhaps for the last time)...we have a larger table with dates rendered as

<span class="pat-moment"  data-pat-moment="format:DD.MM.YYYY" tal:content="entry/created"/>

Applying the patterns caused a browser repaint and table reformatting...visual disturbances even for a small table with only 20 dates. How do you deal with that?

In another project we are using a spinning wheel (https://www.onkopedia.com/de) in order to display the page after applying all Javascripts...

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