You open a SoundFont's instrument/preset data and you change a value.
When you open the piano keyboard to test your changes, the change is not reflected in the sound.
After this intriguing thing happens, you go onto another instrument/preset, but the main part of the display does not change to the new instrument/preset, it stays on the old instrument/preset.
Thinking that there is something wrong, you save the SoundFont, but the changes are not reflected in the saved file.
After re-opening the SoundFont, the issue seems temporarily fixed, until it happens again
https://www.polyphone-soundfonts.com/en/forum/support-bug-reports/364-unstable-issue-of-polyphone-2-0-1?start=6
This bug seems to occur more often on Windows.