SoftBank, the biggest investor in WeWork, is exploring ways to replace Adam Neumann as chief executive, four people familiar with the matter told Reuters on Sunday.

The showdown between the giant Japanese conglomerate and one of its biggest investments comes after the office-share start-up’s parent, We Company, postponed its initial public offering (IPO), following pushback from prospective investors not just over widening losses but also over Neumann’s unusually firm grip on the company.

SoftBank was hoping the IPO would bolster its profits as it seeks to woo investors for its $108bn second Vision Fund. It invested in We Company at a $47bn valuation in January but stock market investor skepticism led to the start-up considering a potential valuation in the IPO earlier this month of as low as $10bn.

The revelations come amid tumult at WeWork. Neumann has been the subject of reporting about drug use and other eyebrow-raising behaviour including reportedly cashing out $700m and reportedly owning stakes in properties the company rents, potentially posing a conflict of interest.

Directors on We Company’s seven-member board aligned with SoftBank are deliberating how to replace Neumann as CEO, the sources told Reuters. Benchmark Capital, another big investor, would also like Neumann to step aside, one source said.

No challenge to Neumann has yet been tabled, the sources said. A We Company board meeting to discuss his future could be held as early as this week, another said.

One option SoftBank is considering is asking Neumann to become interim CEO while a headhunting firm is hired to find an external replacement, the first source said.

We Company and SoftBank declined to comment. Neumann and Benchmark Capital could not be immediately reached.

The Wall Street Journal first reported on SoftBank exploring ways to replace Neumann.

As co-founder of the We Company, Neumann holds special voting shares that enable him to dismiss dissident directors and shoot down any challenge to his authority.

However, SoftBank could choose not to back the IPO or provide more funding. It has already funded the cash-burning startup to the tune of $10bn, and was discussing committing another $1bn to the IPO.

We Company said last week it was aiming to become a publicly traded company by the end of the year.

In a sign of the deteriorating relations between SoftBank and WeWork, Neumann did not participate in a gathering of executives of companies backed by SoftBank in Pasadena, California, last week and was organized by SoftBank’s chief executive, Masayoshi Son, according to two people familiar with the matter.

Son favors removing Neumann, CNBC reported.

Neumann said in a staff webcast on Tuesday he was “humbled” by the IPO delay and had lessons to learn about leading a public company.

The Guardian’s US office is in a WeWork building.

Uber, another loss-generating SoftBank investment, recently went public. SoftBank lost approximately $600m when the rideshare company’s shares dropped, according to reports.

An investment in Slack has also foundered. Shares in the workplace-chat app fell 30% after its IPO in June.