Activist investor group Engaged Capital has escalated the fight with Outerwall, parent of DVD kiosk operator Redbox, urging the board to take the company private and make other changes.

Engaged Capital, which has acquired a 14.6% stake in Outerwall, publicly released a letter sent Thursday to the Outerwall board about its concerns and recommending steps to boost shareholder value.

In the letter, Engaged Capital said the stock’s decline is the result of the board’s “failed strategies, flawed capital allocation policies and misaligned governance.” Over the last four years, the company “has squandered approximately $1.2 billion of shareholder capital,” it said.

Outerwall, in response to the investor’s announcement, said it “welcomes the opinions of its shareholders and remains open to constructive input toward the goal of enhancing shareholder value.”

“While it is unfortunate that Engaged Capital has chosen to initially share its views in a public forum without first discussing them with Outerwall, we will carefully review the Engaged Capital letter and presentation and will continue to maintain an open dialogue with Engaged Capital as we do with all of our shareholders,” the company said.

The agitation from Engaged Capital comes after Outerwall released fourth-quarter 2015 results earlier this month — and issued a weaker-than-expected outlook for Redbox. The company reported a 17% decline in Redbox’s Q4 revenue and said it expects the unit’s DVD rentals to decline 15% to 20% in 2016.

Among Engaged Capital’s recommendations are to retain financial advisers and begin a sales process with the goal of taking Outerwall private. In addition, it urged the company to cease all growth investments, aggressively manage both Redbox and Coinstar for cash, and sell or shut down the ecoATM business. Engaged also wants Outerwall to use the majority of its free cash flow to pay a large annual dividend of $125 million to shareholders and reduce debt.

According to Engaged Capital, on at least three occasions in the last year, Outerwall has refused to engage with potential acquirers, “by either insisting the company was not for sale or simply failing to respond at all to the interested party.”

Outerwall chairman Nelson Chan has refused to meet with the investor “in a timely fashion,” Engaged Capital claimed.

According to Outerwall, since it learned of Engaged Capital’s ownership position less than two weeks ago, its executive management team as well as Chan have “engaged in several discussions with Engaged Capital in an attempt to foster a constructive dialogue and understand Engaged Capital’s specific recommendations, which it has declined to provide in our interactions to-date prior to releasing its public letter.”

The company added that some of Engaged Capital’s recommendations are consistent with many initiatives currently under way, including managing both Redbox and Coinstar for profitability and cash flow.

Engaged Capital, in its letter, said it will use “every method available to shareholders to hold the board accountable,” including nominating new directors at Outerwall’s 2016 annual meeting in June. The Newport Beach, Calif.-based firm says it specializes in “enhancing the value of small and mid-cap North American equities.”