Combining Multiple PDF files into one PDF - Freezing

Used to work perfect, every time. Now it just freezes, basically every time. 

Current process is - open acrobat, help - repair. May or may not work once. If it does work, freezes next time. Close and repair. There has to be a better way, can't continue to use this going forward. I've uninstalled, cleaner tool, etc... tried the recommended fixes on the various searches regarding freezing when combining files. Any help would be greatly appreciated.