repiring old putty in metal windows

[DH05]

The putty is failing on metal casement windows (vintage 1930s). Most of putty is sound, but there are stretches where the paint over the putty is peeling and/or putty is cracked. In a few places, pieces of hardened putty can be removed exposing the metal of the window. Is it possible to patch the putty with new linseed oil based putty, or is it necessary to completely remove all putty? Since most of the putty is sound I'd like to leave as much alone as possible.

Are there better materials for repairing than linseed oil putty?

Thanks!

Moderator 3

I have moved this to Painting & Decorating as they might know the answer