Thursday we reported that T-Mobile's version of the Samsung Galaxy S5 was getting a minor bug fix in the form of a 131 megabyte update. It looks like the cure was worse than the malady, because T-Mobile has abruptly halted the G900TUVU1ANE5 update, putting up a short message on the support page by way of an explanation. 

Updated May 23 @ 8:30 PM EST

The Samsung Galaxy S 5 Software update to G900TUVU1ANE5 via OTA or Kies has been paused. This post will be updated when further details are available.

Details are scarce, but a little investigation from users at the XDA-Developers forum have found a probable reason: some users were seeing vastly decreased data speeds immediately after applying the update.

It appears that many users are having major download issues after updating to yesterday's ANE5 update.  Once the update is applied, download speeds are reduced to 1MB.  T-Mobile may even have pulled the update. - Michael Aybinder, XDA

Informal polling on the XDA thread indicates that some users aren't seeing any issues after the update, while others are seeing dramatic drops in speed and coverage on LTE. Others only see the issue when switching to a non-T-Mobile SIM, so updated modem software may be to blame. In any case, while I'm sure the problem is frustrating for those experiencing it, it's good to see T-Mobile reacting relatively quickly.

Source: T-Mobile Support