On each occasion, the buyers agreed to the sale and paid the defendant in a bank account he provided.
No items were delivered and Chapman broke contact with each buyer.
But after first reporting the scam in early 2016 Vicki Carey became frustrated with a lack of communication from the police and the file being passed around to different stations and officers.
She didn't think police were taking the investigation seriously enough, given there was more than one victim, and ended up lodging a complaint with the Independent Police Conduct Authority in August 2017.
She complained she had to instigate most of the communication.
Vicki Carey, who lives in Blenheim, said she had also been told an alert had been put on Chapman's file but when police had him in custody they failed to question him about it.
Chapman was eventually charged for the offending earlier this year and police apologised to the couple in March followed by a letter from Whanganui Area Commander Nigel Allan.
While the complaint related to the handling of the case in other police districts the file ended up being dealt with in Whanganui.
"As part of that conversation you advised that Detective Heathcote of Whanganui CIB has been wonderful with keeping you updated since he received the file late last year," Allan wrote.
"This is very pleasing to hear but it does not change the fact that prior to this the police let you and your partner down."
Allan said he found the complaint regarding a lack of communication to be justified and apologised.
"The Police failed to communicate sufficiently with you in relation to the progress of the investigation.
"... this gives the NZ Police the opportunity to review our processes to ensure we deliver quality customer service to the victims of crime."
This week Judge Dugald Matheson sentenced Chapman to four months' imprisonment for the charges.
