pattern module makes trouble

How much RAM do you have and how complex is the artwork?

@Kasia Dippel This issue is not uncommon and often points to a problem with either a corrupted preference file, a specific file setting, or a conflict with your system's graphics card. Since restarting and reinstalling the software hasn't solved it, the core issue is likely a persistent file that wasn't removed during reinstallation, or a system-level conflict. The most common fix is to manually reset your preferences, as a fresh reinstallation often fails to delete these hidden user files, which can carry over the bug. This process involves a simple keyboard shortcut during startup to force Illustrator to create a new, clean preferences file.

To reset your preferences using a keyboard shortcut:

• PC: Hold down Ctrl Alt Shift as you click the Illustrator icon to launch the program
• MAC: Hold down Cmd Option Shift as you click the Illustrator icon.

Keep the keys held down until you see a dialog box asking if you want to delete the preferences file. Confirm that you do, and the program will then open with its default settings.