Elon Musk’s purchase of Twitter could go down as the worst leveraged buyout (LBO) deal for banks since the 2008 global financial crisis in the latest worrying sign the deal is proving costly to Tesla (TSLA) shareholders.

While more than half of the $44 billion price tag came from Elon Musk, some $13 billion had to be raised from a consortium of lenders in order not to overwhelm Tesla shareholders after the entrepreneur liquidated billions of dollars in Tesla stock.

Typically, Wall Street banks will underwrite the debt financing from major deals, later packaging and selling the debt on to professional investors like hedge funds and pension plans in a matter of weeks or sometimes months. But the poor timing of the October 2022 Twitter deal, struck just when borrowing costs began to soar, combined with the dire financials of the social media company, soured any appetite on the part of money managers.

Nearly two years on, investment banks have been unable to offload the debt, tying up precious capital and limiting their ability to originate and finance more deals. In fact, no LBO debt has sat longer on balance sheet since the Lehman Brothers bankruptcy, according to new information from PitchBook LCD cited by the Wall Street Journal on Tuesday.

The previous record was 13 months stemming from the 2007 acquisition of car-parts group Tower Automotive by private equity firm Cerberus during the peak of the subprime bubble.

The data does not provide any indication as to whether X had breached its loan covenants, usually the first sign of distress, and the company did not respond to a Fortune request for comment.

But reporting in recent months has indicated that Musk repeatedly sought to assuage banker concerns even as he sought less onerous terms.

Unsustainable debt

When the deal was inked Twitter was expected to shoulder over $1 billion in annual interest, before capital expenditure and operating expenses. That's a problem, given that revenue in its main U.S. market may be tracking to roughly $600 million this year, and even prior to the Musk acquisition, Twitter struggled to monetize its user base.

Fortune reported in October that Musk had held repeated talks with bankers to discuss restructuring the debt to achieve more financially sustainable terms.

According to the Wall Street Journal, however, those talks have come to an impasse. While it remains unclear whether X is currently paying its debt, indications from at least one bank show that this is affecting the lenders’ bottom line.

Thanks chiefly to the legacy Twitter LBO debt, Barclays senior M&A team were informed last year their annual compensation would shrink by 40% over the previous year. The cut was so severe that almost a quarter of the bank's 200-plus managing directors quit once they had collected it.

Musk might still pull a rabbit out of a hat, but X’s financial woes are raising the alarm among Tesla bulls. Last week Halter Ferguson Financial warned that Musk may be forced to sell $1 billion to $2 billion worth of Tesla shares to plug financial cracks emerging at Twitter, now X, with fresh infusions of loss-absorbing equity.

Fortune reached out to Barclays and Tesla for further comment.

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