During Chelsea's 4-3 win against Brighton at Stamford Bridge on Sunday, referee Michael Oliver emerged for the second half missing his communications pack.
For 45 minutes, the Premier League officials had to work without radio sets, which may mark the first time such an issue occurred in 20 years.
BBC Sport understands that crowd noise was not filtering out of the system, making it impossible for the referee and his assistants to hear each other clearly.
VAR Andrew Kitchen had to rely on a back-up system sending messages to the referee's watch, conducting checks based purely on his own video assessment.
