I’ve not heard anything about any upgrades failing. The signal system failed just before close of traffic on Thursday night however trains were still moving on the ground, because this problem could not be sorted the staff moved to the backup control room before start of traffic Friday. During engineering hours a broken rail was discovered and there were Green Park during the AM peak.
Just after 1am on Friday night so the Night Tube Service was suspended to allow systems to be rebooted and to staff to go back to the normal control room. The system then failed again yesterday morning.