Download error: Not enough disk space to install game

I'm having the same issue mentioned in sharkwouter/minigalaxy#448. I'm on Fedora Silverblue 36, using the Flatpak of Minigalaxy. I have more than enough space on my main drive to download and install Stellaris, but when I try to, Minigalaxy throws the error seen in the title. I think it may have something to do with how Flatpak apps cache things, but I have relatively little knowledge in that arena. Any ideas? Here's my `df -h`:

```
Filesystem Size Used Avail Use% Mounted on
devtmpfs 4.0M 0 4.0M 0% /dev
tmpfs 7.8G 0 7.8G 0% /dev/shm
tmpfs 3.2G 10M 3.2G 1% /run
/dev/dm-0 488G 89G 396G 19% /sysroot
tmpfs 7.8G 3.8M 7.8G 1% /tmp
/dev/dm-0 488G 89G 396G 19% /var
/dev/sdb2 974M 82M 825M 10% /boot
/dev/dm-0 488G 89G 396G 19% /var/home
/dev/sda1 938G 750G 142G 85% /var/mnt/Sandisk
/dev/sdb1 599M 9.8M 590M 2% /boot/efi
tmpfs 1.6G 420K 1.6G 1% /run/user/1000
/dev/sdc1 1.9T 1.5T 379G 80% /run/media/miracleorange/WD My Passport
```