The company is planning to increase mine production from 13 million tonnes per annum to 16Mtpa.
"We are working with external stakeholders to address these issues," the company said.
"Yancoal continues to achieve production optimisation at the Moolarben mine.
"The optimisation process continues after receiving federal government approval to increase open cut mine production in September 2019."
The company said its current focus was a modification application related to the underground operation, submitted in Q4 2019.