Legacy Title causes extreme lag on Premiere Pro

I don't know what's going on, but suddenly Legacy Title is causing extreme, insufferable lag on Premiere Pro. The frame rate drops to 2fps, and all the controls become very unresponsive and laggy. 

I was in the middle of editing some clips, and I didn't have any problems until I used the Legacy Title. 

So I thought maybe something was out of wack, so I closed everything, shut down the computer, and then restarted everything. I opened Premiere Pro and tried opening a new project and importing one clip. It played fine. And then I just added a basic legacy title and wrote "test." As soon as I do this, everything slows to a crawl. Even after I delete the legacy title, the damage has been done. 

Only way I can get Premiere Pro to act normal and fluid again, is to close the program and open it all over again and not add any more legacy titles. 

This did not happen before. I used to be able to add 50+ legacy titles to a video without any problems. Now I can't even add one legacy title without Premiere Pro becoming paralyzed. 

Anybody know what's going on? 

PS: I just checked which version I had, and I have 12.0. Is this why? Should I update to the new version? I don't understand why the older version would be affected by updates, though. 12.0 worked perfectly fine before.