You call it "the app" as if you're on a mobile device such as an android. However, you clearly state you're Windows 10. So I'm assuming you are on a full fledged windows computer and not something like a Chromebook or some other cheap throw-away technology.
I've been using multiple versions of the CD/Desktop software on my windows 10 pro computers (3 of them) and no issues with stability at all. I strongly suspect you have other issues. So here's some wild guesses of things to try based on no facts what-so-ever.
- After physically disconnecting the computer from the Internet, disable "real time protection" on whatever antivirus program you're using. If using a separate malware program, turn that off too. Then use the TTX program and see if remains stable with the antivirus turned off. If it does, then you potentially have issues with the antivirus.
- Make sure that either Controlled folder access is turned off (which I do not recommend you leave it off) or that C:\Program files(x86)\TurboTax\[yourversion]2018\32-bit\turbotax.exe is allowed to bypass controlled folder access.