Siemens Energy shares plunged 31% on Friday morning after the company scrapped its profit forecast and warned that costly problems at its wind turbine unit could last years.

The company, born from the spinoff of the former gas and power division of German conglomerate Siemens, announced late on Thursday that a review of issues at subsidiary Siemens Gamesa had found a “substantial increase in failure rates of wind turbine components.”

The Siemens Gamesa board has initiated an “extended technical review” aimed at improving product quality that the parent company said will incur “significantly higher costs” than previously assumed, now estimated to be in excess of 1 billion euros ($1.09 billion).

“It is too early to have an exact estimate of the potential financial impact of the quality topics and to gauge the impact of the review of our assumptions on our business plans,” Siemens Energy said in a statement.

“However, based on our initial assessment as of today, the potential magnitude of the impact leads us to withdraw the profit assumptions for Siemens Gamesa and consequently the profit guidance for Siemens Energy Group for fiscal year 2023.”

Siemens Gamesa has long been a thorn in the side of its parent company since its full takeover late last year.

Siemens Energy CEO Christian Bruch told journalists on a call Friday that “too much had been swept under the carpet” at Siemens Gamesa and that the quality issues were “more severe than [he] thought possible,” according to Reuters.