This is exactly as expected with the Visionaire engine. If the variables are already there that part will play even with old saves. But new parts require new variables and as you see for yourself those don't work. The coin is there, but it is a new one, so a new set of variables which controls the things like did you pick it up, to unlock the correct extra scene with Brenda etc.
So never (!) use old saves. They are available, so complain to the person who uploaded a broken game. Or consider becoming a Patreon. This is easily the best game ever. I see that more and more Ren'py games try to animate things. But in Willy a sex scene means at least five positions each with a animation. The mentioned Ren'py games are also bcoming bigger, so you can calculate what 14,7 GiB of animations does
.Ones every tow to three months I start from the beginning and that is a punishment or becoming boring. Every time I discover new things like a funny dialogue about a sign or pidgeon.
