Fault code 3751

[gemarsim]

It s not being much activity on this topic recently but I'm having similar issue right now. Same codes with No Check engine light on. Code 3751 spn 4792 is active and force regen does not come to an end by itself after 90+ minutes in two consequential tries.
Recently I am getting 3383 inactive EGR system date a valid but above normal operating range moderately severe level.
I have never tried to do something with the DPF or catalytic converter never open the tubes.
Never had an issue with clogged filter after almost 200,000 miles which I put on the truck for couples years now is close to 600k miles.
Am I wrong if I think I have to replace the catalytic converter which is close to three thousand dollars and bake the filter?
Any other suggestions will be greatly appreciated.