Ah, so you are using the experimental build of Universe Sandbox. Thanks for mentioning that. The experimental build is not finished. There are sill many bugs lurking around. Perhaps this build is not optimized yet for Mac OS operating systems.
If you cannot afford to buy a new PC, you can download free iso image copies of Windows 10 from the internet. You will need to find a full product key. When you find the .iso image file of Windows 10, download it first, then burn it to a DVD/USB/SD Card or hard drive. Next step will be to reboot your machine and install a fresh copy of Windows 10 on your hard disk. First remove Mac OS, by deleting the hard disk partition(s) and install Windows 10 as a brand new installation. When finished, try to run Universe Sandbox again with the experimental build and try again to see if your problem is solved.
Please note that you will need to re-install all your software applications, apps and drivers after the new installation of Windows 10 is complete. If you find any Windows 10 bugs, use the feedback hub to report any bugs you find to Microsoft. You will need a Microsoft account to submit feedback and complaints to Microsoft.
I hope I helped you out. If you need more help, I'll be glad to help you further. Just give me a shout and I'll help you out.
Good luck, and enjoy Windows 10 and Universe Sandbox.