It was the big announcement at this year’s WWDC: Apple is switching from Intel’s processors to ARM chips it has developed itself. One of the reasons for this may have been poor QA (quality assurance) from Intel, and specifically the problems it’s had with the Skylake architecture.

François Piednoël, a former Intel engineer, tells PC Gamer that Apple was deeply dissatisfied with the company’s products after Skylake was introduced in 2015.

The QA of the processors must have been unusually poor, because Apple reported more complaints than any other company for the Skylake architecture, he adds, and goes so far as to claim that Apple discovered more bugs than Intel itself. He described Intel’s quality assurance as “abnormally bad” at the time.

Piednoël speaks from a position of authority: he was an engineer at Intel for almost 20 years. Today he works in the research and development team at Mercedes Benz.

Apple’s first Mac with Skylake processors was the 2015 iMac; the 2016 MacBook Pro also came with Skylake chips. They can still be found in the iMac Pro today. The first ARM-based Mac is expected to be a Mac mini for developers, but the first consumer product may be a 12in MacBook.

The Skylake problems are certainly not the only reason Apple is leaving Intel; having greater control over more of the components in its Macs is believed to be a major factor. But if Piednoël’s comments are accurate, QA worries could have tipped Apple over the edge.

Based on articles that originally appeared on Macworld Sweden and Macwelt. Translation by David Price.