I have the same things on Debian, if I use a titleblock variable used by cartridge also and if I use conductor formula PE-%id-%{volta} the formula didn't work, so I double click on conductor and replace {} by () and it matchs at moment also then you re open it didn't work .
but if variable isn't a tiitleblock use {} for your conductor formula..
I don't know what as changed, maybe Qt 5 version Qt 5.15.10....?, or lastest merge...?
So I also have the same problems on my Debian Oho... So I recommend to use {} for your formula..
Edit: isn't a Qt framework problem, just tried with latest AppImage I have builded and I saw the same problem, formula didn't work, ok after saving project closed and re open project..
Ps: AppImage is only Qt 5.15.2 version.
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