Is your system fully up to date? as that error message should not appear in new versions as a bug fix has been applied.
Perhaps try this solution:
Memory leaks in plasmoids are common. Uninstall any plasma widgets you are using one at a time to try and eliminate that as a possibility.
That error message is actually of little importance and not a great concern (it should be removed in new versions).
Just read the reddit post you linked. It basically says the same thing I already stated. Eliminate your plasmoids one by one to eliminate that as a cause. Have you done that yet?
Also, the reddit thread did not resolve the question of if there actually was a latte memory leak, but as the thread was 2 years old it’s not exactly relevant in today’s conversation because of its age anyways.