The Upholder-class was designed to meet a late 1970's RN requirement for a diesel-electric replacement for the Oberon-class subs, with the lead boat being laid down in late 1983 following the selection of the design the month before.I believe these boats were constructed in the late 1980s and didn’t enter service until 1991 and were all mothballed by 1995. The RCN didn’t begin to use them until around 2000. The main issue was they didn’t age well during storage. It is still my belief the RCN knew their condition was not optimal but honestly believed if they didn’t push for the acquisition the RCN would have been out of the sub business. Chrétien was ok pi$$ing away 500 million on helicopter cancellations but committing money for new subs...not so much. Four new boats in 2000 would mean a no financial stress replacement in 2035-40 after the fighter replacement and CSC. Chrétien was a senior brown-noser and an advisor to junior.
An impression I have formed is that either the subs were wired/built with some obsolescent components, had some build defects, or were "used hard and put away wet," or perhaps even a combination thereof. This impression comes from comments made by GF in the past about an Australian/RAN inspection of the Upholder-class subs when Australia was looking at replacing their O-boats, prior to settling on a (mostly) domestic build of a new sub class.