Sticking points include the differential, thought to be in the region of 10 pence per share, between the price former employees have been offered for their shares and the 72p per share price offered to current employees.
In addition current employees will be given the opportunity to retain shares in the new company, following the sale to Lake Capital, while ex-employees have only been given the option to sell their shares at the lower rate.
Shareholders received letters today (Friday) outlining details of the offer, with those receiving the lower offer now calling for a fairer deal.
One shareholder told PRWeek: "The announcement of the sale [to Lake Capital] seems very premature because a third of shareholders are yet to agree to the offer."
The rules of the prospective sale are that 75 per cent of Engine’s shareholders have to agree and if a third are unhappy with the offer, it raises the prospect that the deal could be scuppered.
The shareholder said there had been no formal consultation on the terms of the deal and added: "We feel the offer is unfair because the two sorts of shareholders are being offered different deals. All we are seeking is a fair deal. If those shareholders who wanted to were able to retain their shares in the new company, they could be worth a lot more in the future. This is not a great time to be getting out with the recession now over."
The shareholder would not be drawn on what action those who are unhappy with the deal would take if the offer was not improved, but a second shareholder went further.
The second shareholder said: "Unless fair value is received by all Engine shareholders, a number of us would prefer to see Engine Group retain its independence and seek a different deal in the future that offers fairness for all shareholders."
A spokesperson for the Engine Group said: "The Board of Engine has carefully considered the strategic alternatives open to the Group and has concluded that the offer from Lake Capital is in the best interests of all stakeholders - shareholders, employees and clients.
"The offer document which has only just been mailed to shareholders explains the Board’s thinking in some detail."
This article was updated on 4 August with a comment from the Engine Group.