SRT bound for Suiseo from Busan turns back to Busan Station 10 minutes after leaving the depart... ”Cause under investigation”

An SRT (Suseo Rapid Transit) train that departed from Busan Station and was heading to Suseo Station in Seoul canceled its operation due to an unknown issue and returned to its departure point.
According to SRT's operating company SR, the SRT departed from Busan Station and headed for Suseo Station at around 4:43 p.m. on the 8th, but stopped operating just before entering the Geumjeong Tunnel.
The train returned to Busan Station. It was discovered that there were about 190 passengers on board. SR then sent a replacement train to Busan Station at around 5:27 p.m., and the delayed arrival
The train was returned to Busan Station on March 18, 2019, and the passengers were taken to a nearby train station on March 19.