I keep breaking belts on my 38" deck, the outside of the belt rubs against the front deck bracket when making left turns. It seems like when it's free floating the deck moves too much side to side.
Post your 7 digit Regent model number, example: 1692182. Possibilities include deck belt worn out, idler pulleys & bearings worn out, loose hardware, idler arm cracked.
Check the wheels at the back
Been a couple of Simplicity owners with a similar problem.
Both of them had loose or broken mounting bolts on the rear of the deck which allows the back to drop and the deck to twist enough for the bracket to hit the pulley.
Check the last 5 threads in the Simplicity section for the details.