A particularly frustrating variant of the 'piano wire' issue:
A redundant pair of devices, except cables have been run in such a way that if one device failed, you could not remove it from the rack without removing cables from the remaining device.
this is the reason why (ideally) you should have three racks in a redundant setup:
2 for redundant component placement (with redundant power obviously).
1 for interconnections between the racks, having prepared cabling and MPO panels installed to make interconecting devices easily, without having to change anything in the equipment racks compared or vice versa.
Makes replacing hardware a breeze, and prevents a lot of issues with cable mess inside equipment racks because those cables are very short to MPO panels.
A redundant pair of devices, except cables have been run in such a way that if one device failed, you could not remove it from the rack without removing cables from the remaining device.
/facepalm