I have this issue since the introduction of cloud saves. One save of mine is 3gb.
The only solution i found was to copy the unzipped save manually to the game folder (media_soviet/save_cloud), but you need to check if you have cloud space available, as the unzipped save can get a little large.

Yes, I considered manually copying the latest save file to a USB and transferring it to my laptop, but that defeats the whole purpose of having seamless cloud-based save syncing

I dont mean manual transfer through Usb. I mean copying the file from /save to /save/cloud. Somehow this works, while the save function inside the game doesn't.