Not major but...
Many years ago the factory where I worked lost power on one phase, unfortunately the one with most of the offices on. It wasn't a major issue, just the main fuse blown but getting it replaced took several hours:
Engineer attends, can't get the dead fuse out, calls it in and leaves.
The heavy mob are sent from another job and remove the fuse in about 30 seconds, but aren't authorised to work on live equipment to put the new fuse in so they call it in and leave.
A senior engineer arrives to check our load balancing across the phases as they suspect that may be the cause (it wasn't, the issue was a slightly loose fuse overheating) which he can't do without the fuse in but fortunately he was authorised for live work and happened to have his kit with him so he fitted the new fuse then did his balancing check.
He reported there was an imbalance that we should investigate but it wasn't major - that was simply that as soon as he'd inserted the new fuse all the hand driers had started up!