Hi @Sofia25629549ta0q,
I'm sorry you're running into this issue. Could you confirm the version of InDesign you're using and share details of your operating system? I tried locating any crash reports linked to your community email but couldn't find any. Please submit a crash report via the Adobe Crash Reporter dialog box and share the email address you used while submitting, so I can check the logs: https://adobe.ly/479gXl1
In the meantime, please try the troubleshooting steps in these articles, as they may help resolve the problem: https://adobe.ly/3JfcVNP and https://adobe.ly/4fsrucW.
If the issue continues, try exporting your document as an IDML file and reopening it, then test splitting and unsplitting columns again. You might also see if a specific frame or content is triggering the crash by testing with a new text frame containing simpler content.
Looking forward to hearing back from you.
Abhishek