Much of the 70 billion pound UK property fund sector was suspended in March after surveyors said it was not possible to be sure about valuations due to the COVID-19 pandemic.
Several asset managers, including Columbia Threadneedle, St James's Place, Legal & General and BlackRock, have reopened their funds in recent weeks, as that valuation uncertainty eased in September.
"Now that so many property funds have reopened for business, the big redemptions are simply a shake-out, as those investors wanting out of real estate assets finally have an opportunity to retrieve their capital," said Edward Glyn, head of global markets at Calastone.
Calastone said the sector had only seen more monthly outflows on two previous occasions - Dec 2019 and Dec 2018.
The value of sell orders was eight times higher than buy orders in October, it said.
The previous low point for buy orders was in July 2016, a month after Britain voted to leave the European Union, when sell orders outnumbered buy orders by five to one.
"More redemptions are likely until the pent-up appetite to sell has been sated," Glyn said.
Calastone did not name any of the real estate funds it tracked. More than two-thirds of UK-domiciled fund flows by value cross its network each month.
Columbia Threadneedle, which reopened its fund in mid-September, said it saw 74 million pounds in net outflows in September. The Threadneedle UK Property Authorised Investment Fund has 940 million pounds in assets under management, according to Morningstar.
(Reporting by Carolyn Cohn; editing by Sinead Cruise)