We're currently using renpy ver 7.8.4. Hopefully that's not a huge issue.
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renpy's latest version is 8.4.1 so it might be a problem.
Updating the entire engine may cause issues. (hopefully not cuz the renpy devs are cool like that)
I know it might be a little time consuming, but a fresh, updated install of everything might be the way to go.
(If you install the newer engine separately instead of upgrading, you could copy all the game files over for testing without making any permanent changes)
But please take my advice with a grain of salt and see if the reddit gods are on your side and someone else with this issue has been given a better answer.