1) In June 2007 there was a major computer failure on International Space Station, which
left the station without thrusters, oxygen generation, carbon dioxide scrubber, and other environmental control systems, causing the temperature on the station to rise.
The root cause of the failure was found to be
[the] condensation inside the electrical connectors, which led to a short-circuit that triggered the power off command to all three of the redundant processing units.
This article by James Oberg, a 22-year veteran of NASA mission control, explains in details the sequence of events and factors contributing to the computer failure (moisture condensation and design fault that allowed powering down all three redundant units at the same time); and claims the use of gray (duct) tape when securing an improvised thermal barrier in order to aid in protecting the replacement computers from moisture:
They [the cosmonauts] also decided to rig a thermal barrier out of a surplus reference book and all-purpose gray tape.
2) The famous case of discovering the hole (August 2018) in Soyuz MS-09 spacecraft docked to ISS.
This news article reports the use of duct tape as a temporary measure to cover the hole (although wikipedia MS-09 article refers to the tape as "Kapton tape"):
European Space Agency (ESA) astronaut Alexander Gerst initially plugged the gap with his finger, before using duct tape to cover the hole, preventing more air leaking into space.
Later, the two Russian spacemen put sealant on a cloth and stuck it over the area.
This article cites Chris Hadfield's tweet:
When your spaceship suddenly starts leaking air, you fix the hole with duct tape & a gob of epoxy. Nice save, @Space_Station crew!