Hi to you from David.
It sounds to me like the defrost timer had to run its course and then all worked ok again. Often the electronics of these modern refigeration appliances have delays in them, by which if you switch the appliance off for any period of time and then back on again, you have to wait usually about 30 minutes for it to start to run correctly again. I would say this was quite normal.
Lots of strangeness regarding fridge. First, having to defrost "frost free" fridge, then having "repair" result in no cooling. Refrigerator is 28 yrs old. Doubt it has any electronics. Why did compressor and condenser fan fail to come with evap fan on all night with new timer? Why, when I plugged i old timer, did the compressor and condenser fan come on immediately, yet evap fan start was delayed? Is new defrost timer defective?
No I would not think defective for one minute, but you could of advanced defrost timer manually when fitted