Doors and Windows - exterior door handset

On my front door to my house I have a deadbolt and then a Wiser handset. The handset has the push down lever on the outside and then a regular knob on the inside to turn it. Over the last few months the door was difficult to open by pushing down on the lever unless you pulled back on the door. Today my son phones me and he can't open the door from the inside cus it just turns but nothing happens.
I came home and I was able to get the handset off and remove it. It would appear the 'assembly' that slides the bolt back and forth is not working properly (at least to the untrained eye).
My thought is to just replace the handset as it will be easier, but more costly, so I guess I just wonder if based on my description it is possible to give some advice on how to fix it.

Unless the lockset is very decorative, and you think you can find a similar replacement, I would go that route. Trying to fix the guts of one will set off your arthritis and make your blood pressure go wild. I would replace both the deadbolt and the lockset at the same time so you can get them keyed alike and they will match in design/color.

As it turned out I was able to just get a replacement bolt assembly from a locksmith store and it is working so far.
Thanks.