I made an error in a proof

I’ve proved the following (for every funcoids $latex f$ and $latex g$):

Statement $latex \mathrm{up}\, (f \sqcap^{\mathsf{FCD}} g) \subseteq \bigcup \{ \mathrm{up}\, (F \sqcap^{\mathsf{FCD}} G) \mid F \in \mathrm{up}\, f, G \in \mathrm{up}\, g \}$ or equivalently: If $latex Z\in\mathrm{up}\, (f \sqcap^{\mathsf{FCD}} g)$ then there exists $latex F \in \mathrm{up}\, f$, $latex G \in \mathrm{up}\, g$ such that $latex Z\in\mathrm{up}\, (F \sqcap^{\mathsf{FCD}} G)$.

But now I’ve noticed that the proof was with an error! So it is again a conjecture.