Is Orca wrongly breaking bonds? Why can it only optimize the molecule with COPT activated?
It seems to be a bug with optimization in internal coordinates. As I already mentioned in comments, ORCA couldn't converge at geometry relaxation step when optimization is done in internal coordinates. Switching to optimization in Cartesian coordinates (coordsys cartesian) or old internal ones (coordsys redundant_old) in the %geom section of the input, or using the ! COPT simple input as OP has done, solves the issue.

P.S. OP might report it as a bug at ORCA forum so that developers can take a closer look at this case.