Oh I had one of these only a couple of years ago.
The Deputy head of the 6th form college I worked for was teaching in a lab classroom when all laptops\desktops were reduced to a crawl after I kicked of a 2TB file transfer from a DR Backup Exec server to a New DR file server. There were a good 100 end point connected to the edge switch stack trying to login with roaming profiles at the time my file transfer was saturating the link. The lab was next to the DR room I was in so I heard the uproar at the issues and quickly terminated the file copy and popped into the room to check everything out. NP all sorted now, I'll investigate and let you know later if I find a root cause.
Turned out a predecessor in my sysadmin role had run out of MTRJ connectors to patch the Backup Exec server into the core switch (as was the habit at this establishment) and had patched it into an edge switch stack with Cat 6 instead. Server had 2x 1Gbps links back to an edge switch which only had 1Gbps uplink to core switch.
On a positive note the core switch upgrade that happened the next summer had no issues getting approval for all the edge stacks uplinks to be upgraded to redundant bonded links. Needless to say I fixed the server patching later and when I finally left that job they had proper Top Of Rack switching for servers with high speed links back to an upgraded core switch infrastructure that no longer used MTRJ fiber connections. They'll not be breaking things that way again without serious mistakes by onsite staff for some time I hope.