elder mermaid has no tail, swim like regular sim

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.63.136.1010
What expansions, game packs, and stuff packs do you have installed? All
Steps: How can we find the bug ourselves? Mermaid sim turned into elder and when going for a swim in the ocean suddenly has no tail
What happens when the bug occurs? Mermaid sim turned into an elder and went swimming, but suddenly could climb the Island Living ladders into the ocean (mermaid sims can't do that) and swims around like any regular sim (no tail, in normal swim outfit instead of the mermaid one). Still has the hydration instead of Hygiene and still has the CAS mermaid form
What do you expect to see? mermaid sim still having the full mermaid form when going swimming and not being able to climb those island living ladders
Have you installed any customization with the game, e.g. Custom Content or Mods? Not now. I've removed them.
Did this issue appear after a specific patch or change you made to your system? No

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the bug started today, the moment the mermaid sim became an elder. (never played with mermaids before in elderly stage, so I don't know whether this is a regular thing or not)