When you change the font size with commands like \Large inside a group you must end the paragraph either with a blank line or \par before the group ends to get the right line spacing.
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1 2 3 4 5 |
WRONG: {\Large some large Text} Normal sized text |
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1 2 3 4 5 |
RIGHT: {\Large some large Text\par} Normal sized text |
TeX always uses the baseline skip settings of the site active at the paragraph end, which is actually \normalsize in the first code.