Some shapes you're supposed to build do not render in the milestones or tasks menu (including the active/pinned milestones/tasks).
When you click them (or rather the empty spot) and the detailed view opens, they are visible, but the preview stays invisible.
The bug doesn't appear to be savegame specific, as I could reproduce it in a new run as well.
I tried reloading the savegame with no effect and restarting the game resulting in different shapes (not) rendering then before.
The bug appears to be linux (native) specific although, as I couldn't reproduce it when I switched to proton.
System information:
OS: Arch Linux (6.15.6-arch1-1)
CPU: AMD Ryzen 9 3950X
GPU: AMD Radeon RX 9070 XT
DE: KDE Plasma 6.4.3 (Wayland)
I hope this helps