TI stopped updating TI-Nspire CM OSes with version 3.2.0.1219 almost three years ago.
Meaning that you can't open many recent TI-Nspire documents.
Fortunately, we've now updated nsNandMgr to allow modding of TI-Nspire CM into TI-Nspire CX in a more secure way.
Moreover, we have also updated Nlaunch CXM with support for more recent OSes.
As a result, you can at last update your TI-Nspire CM using a TI-Nspire CX OS up to version 3.2.4 or 3.3 !
And you can still install a TI-Nspire CX CAS OS on a non-CAS TI-Nspire CM.
More recent versions like 3.6 although supported by Nlaunch CXM don't work. They fail with the same symptoms as when you try to run a 3.6 CAS OS on a non-CAS calculator.