Donald Trump’s hiring of pollster Tony Fabrizio in May was viewed as a sign that the real estate mogul was finally bringing seasoned operatives into his insurgent operation.

But the Republican presidential nominee appears to have taken issue with some of the services provided by the veteran Republican strategist, who has advised candidates from 1996 Republican nominee Bob Dole to Florida Gov. Rick Scott. The Trump campaign’s latest Federal Election Commission report shows that it is disputing nearly $767,000 that Fabrizio’s firm says it is still owed for polling.

Trump campaign officials declined to provide details about the reason the campaign has declined to pay the sum to Fabrizio Lee, the pollster’s Fort Lauderdale, Fla.-based firm. “This is an administrative issue that we’re resolving internally,” said senior communications adviser Jason Miller. Fabrizio did not immediately respond to requests for comment.

Fabrizio was an ally of former campaign chairman Paul Manafort, who persuaded a skeptical Trump in the spring that he needed a professional pollster. The abrupt departure of Manafort in August and Trump’s hiring of pollster Kellyanne Conway to be his campaign manager raised questions about whether Fabrizio would stay on. There have also been multiple reports that Trump and his son-in-law Jared Kushner have rejected Fabrizio’s advice.

Even though he was hired in May, the campaign did not make any payments to Fabrizio until September, when his firm received nearly $624,000, federal filings show. Trump’s finance reports show that the campaign owes the firm an additional $55,300 on top of the $766,756.67 in debt that it is contesting.

Fabrizio’s polling firm has also been paid by the Committee on Arrangements for the 2016 Republican National Convention, which gave it $273,378 in July, federal filings show.

Despite his issues with Fabrizio, Trump appears to have warmed up to pollsters in general. Since late August, the GOP nominee has tapped four other polling firms to conduct voter surveys, including Conway’s, which had been paid $673,000 through Oct. 19, filings show.