Hotpoint TDC30P Not staying On

I have a TDC 30P that has decided to intermittanly switch itself off. Have done a visual on the relay and it latches with power applied. Only to ‘drop out after anything from 2 min to 20 min. The machine runs if the switch is continously depressed ( have already advised she who must be obeyed not to do this – as lots of juice thro the switch ain’t good). Relay fed from timer unit, so does the fault lie with relay or timer unit? Have seen similar post relating to another condenser that pointed to relay but that reported fault was 5- 20 secs.
Any help please before I make a costly purchase.