In a trading update yesterday, the company said that it had faced operational challenges in the final stages of a £10m project to improve the Scottish site (near Glasgow).
It said this had led to capacity issues and costs to the business in the first half of this year.
However, the project is due to be completed in the next few weeks, and A.G Barr said it expected a gradual improvement in production capacity and efficiencies over the coming months.
A.G. Barr has been restructuring its production facilities, selling its Mansfield plant in June and with the sale due to complete in August.
It is also investing in its remaining sites across the country, including a plant in South Wales used to produce Rubicon Tetra-paks.
The company said it had performed consistently and in line with expectations in the first half of the year. A.G Barr expects sales to be up around 3.5% year-on-year to £123m.
“We look forward to the second half with cautious optimism and the full year remains on track to meet our expectations," it said.
The company will announce its interim financial results for the six months to July 30 on September 27.