Don't get your head in a spin!
Jelly, &nbsp;12 10 8&nbsp; 7 bytes

-1 thanks to dylnan (use of repeat, ¡, as a replacement of if, ?, saving the need for identity, ¹.)

ḲṚṫ¡€5K


A monadic link taking and returning lists of characters.

Try it online!

How?

ḲṚṫ¡€5K - Link: list of characters
Ḳ       - split at spaces (gets words)
     5  - literal five
    €   - for €ach word:
   ¡    -   repeat:
  ṫ     -   ...number of times: tail (5th character on, if empty falsey-&gt;0, else truthy-&gt;1)
 Ṛ      -   ...action: reverse
      K - join with spaces




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Previous 12s: ḲµUµL€&gt;4Tµ¦K and ḲµṚ¹L&gt;¥?4µ€K