Subaru has been enjoying record sales for years now in the US but apparently this success applies big pressure on the company’s facilities in Japan.

AutoNews reports that Subaru admitted that in some of its Japan-based facilities, thousands of workers were forced to work overtime without getting paid for it.

Subaru has since reimbursed the affected workers and said that this impacted only a small portion of its 17,000-strong workforce in Japan.

One of the workers was reportedly forced to work up to 105 hours of overtime in a month, while quality control is also suffering, partly because demand for new Subaru models exceeds the current supply.

The Japanese automaker has been plagued with production issues over the past few months -even resulting into a temporary production halt in its Yajima factory.

Subaru’s struggle has started to affect the U.S. market for a few months now. “We continue to be concerned that (Subaru) is not making the necessary investments and changes fast enough to ensure that vehicles are being produced with the quality the brand and its customers deserve,” the company’s U.S. National Retail Advisory Board wrote in a resolution to Subaru’s high-rank executives in the U.S and Japan on September 18, 2018, following the recall of the US-built Ascent SUV.

In addition, Subaru CFO Toshiaki Okada said that the increased demand should have forced the company to increase their capacity “accordingly in terms of management and facilities” but they simply didn’t. Apparently Subaru is only now looking for ways to start the necessary expansion.