TARDIS system reset

The TARDIS reset system was a system in TARDISes that would allow it to reset and reboot if it has stopped functioning properly. The process would require any crew to leave the vehicle for a lengthy period of time. When activated, it would put out a force field and everything stuck in said force field would be stuck in a time loop until the TARDIS had properly rebooted. (TV: Eve of the Daleks)

System damage
Due to the Twelfth Doctor's explosive regeneration in the TARDIS, the TARDIS became damaged to the point that the click of a single button would cause a "Multiple Operations Failure” and would eject any passenger before undergoing a fiery destructive explosion, dematerialising in an attempt to avoid destroying anything else, (TV: Twice Upon a Time) an event the Thirteenth Doctor termed "Dematerialexploding". (PROSE: Things She Thought While Falling)

The TARDIS would locate itself on the planet Desolation in the Twelve Galaxies in ancient times before it first became inhabited. It was here that the first settlers discovered it phasing in and out of existence every thousand rotations of the planet and, not knowing what it was, dubbed it "the Ghost Monument". It spent the next many millennias repairing itself, waiting for the Doctor to pick it up, seeing itself become the end goal of a Rally of the Twelve Galaxies, eventually being found by the new incarnation of the Doctor, with a brand new control room. (TV: The Ghost Monument)

Although it seemed to be fully repaired, it appeared to still be having some issues, as when the Doctor attempted to return Ryan Sinclair, Yasmin Khan and Graham O'Brien to Sheffield, with Graham remarking upon their landing in 1955 Alabama, that it had been fourteen failed attempts. (TV: Rosa)

In early 2020, the Doctor had taken the TARDIS to a car repair shop and while on the phone to her Team TARDIS, she was repairing the bottom of the TARDIS with some tubing.

It would seem that the shield was also in a weak state as when the Kasaavin were seen to enter through the locked doors (TV: Spyfall) as well as the Judoon being able to teleport themselves inside with no problem. (TV: The Timeless Children)

The TARDIS also took a longer time to travel to some locations, such as when it arrived back on Earth in Sheffield 10 months after Team TARDIS themselves, and took 4 minutes to get to Osaka, Japan. (TV: Revolution of the Daleks)

Malfunctioning
As the new threat the Flux began to terrorize the universe, it also damaged the Mouri on the planet Time, who were in charge of keeping time and space in order. As the Web of Time began to break down, it caused the TARDIS to begin to heavily malfunction, with multiple doors appearing, crystals sprouting everywhere and cobweb covering pillars and more. (TV: The Halloween Apocalypse - The Vanquishers'')

Finally having time to fix the TARDIS, the Doctor landed on the sentient beaches of San Munrohvar where she thought she thought her, Yaz and Dan Lewis could spend some time while the TARDIS repaired itself. She pulled a few levers which caused the TARDIS to flash in disco lights while the cogs started rotating and the controls and crystal pillars initiated repair mode. The Team ran out as the TARDIS threw up a huge force field and red cracks appeared on the police box shell. As it repaired, it threw the surrounding location and people into a time loop. (TV: Eve of the Daleks)