A Blantyre man lost the plot after his face mask snapped and fell off.
The mishap led to Kieran Daly hurling a torrent of abuse and threats at his partner.
Daly, 28, of Roxburgh Place, appeared at Hamilton Sheriff Court this week.
He admitted threatening or abusive behaviour towards the woman on Hillhouse Road, Hamilton, on July 23.
The court heard the couple had been together for four years but argued after a family gathering.
Clare Green, prosecuting, told the court: "They were walking along Hillhouse Road and went into a Shell garage.
"The accused's mask appeared to snap and he became angry, shouting at his partner.
"She walked away but he followed. She made video recordings of him with her phone and told him not to walk so close to her."
The court heard Daly then subjected the woman to verbal abuse and threatened to "smash" her and her family if they did not leave Blantyre.
He also warned he would slash her father's face.
The woman eventually called the police.
Defence agent Ali Murray said both parties are keen to put the episode behind them and "resume their relationship".
He added: "This started as a silly argument, but it spiralled into something more sinister and concerning.
"He thought she was mocking him by filming him."
Sheriff Thomas Millar fined Daly £170 but said a non-harassment order was unnecessary, given the woman's attitude and Daly's lack of previous domestic offending.
He told the accused: "This might have been a silly argument but the court's experience is that these things can escalate into something a lot more serious."