Alex Marshall, president of the IWGB, said the cases were “among the more egregious examples of a gig economy that is increasingly squeezing workers as much as possible and then just dropping them without any accountability.

“The decision to use this GPS system is about cutting costs for Stuart but the ramifications for couriers are huge,” he suggested.

“People are losing their livelihoods in an instant and those that are still working are putting their lives at risk.” Evidence shared with the Observer suggests Stuart brought its GPS system in-house as a cost-cutting measure and that it is aware of problems.

In a direct-message conversation on Twitter, shared with the Observer, a Stuart senior manager can be seen telling a courier: “Stuart has an internally built directions service and it’s not great. We used to use Google Maps directions but they put the price up 10x.”

When the courier replies “people get terminated for allegedly deviating from routes and you just said it is wrong”, the manager acknowledges: “it’s not perfect yes [sic].”

Until May, Adnan Odawa, 35, worked full-time for the app-based Stuart, beginning each day at McDonald’s in Sutton Coldfield. One Tuesday morning he made the 10-mile cycle ride from his home in Birmingham as usual, taking out his phone on arrival to log in to the app as he had done for the past three years. But that morning, he had a new message: his account had been terminated and his access to the platform blocked.

In a pro-forma email seen by the Observer, Stuart told Odawa that several of his deliveries had been “flagged for severe delays caused by excessive detours”, including three order numbers listed in the email.

Odawa did not recognise two of them and the third related to a job where he had arrived on time and made the delivery but, he says, the in-app GPS incorrectly located the address, forcing him to cycle almost a mile to the wrong location to mark the job as complete. “I was shocked,” he said. “I thought: ‘If you’ve got a problem with me for the first time in three years, you could at least send me a message and let me know.’”

For Odawa, conceding to the GPS was the only option. The app includes a chat function for couriers to resolve problems on shift, but when Odawa used this previously he had been left waiting for up to an hour, unable to get through to a human.

Screenshots shared with the Observer show couriers similarly pleading their cases to the chatbot, which repeatedly replies: “No worries, an agent will take it from here” and: “This is an automated message, please do not reply” before asking them to rate the conversation by clicking on an emoji.

After his employment was terminated, Odawa repeatedly emailed Stuart but received only standardised emails in return, stating that his request for reinstatement had been denied and the decision was final.

Marshall said the IWGB had investigated 55 cases since March 2021 and that, in most instances, couriers were given no opportunity to review the decision with human involvement.

An online appeal form was introduced in late 2021 after union campaigning, but it states terminations will only be reviewed where couriers can provide “objective proof” they were not at fault. Stuart can legally dismiss couriers without warning or reason as they are classed as independent contractors, not employees.

Screenshots and photographs shared with the Observer show a driver in Plymouth being routed through a building site, with warning signs visible, and a south-east London driver being sent through a road closure. Others show a driver in east London being directed to break traffic rules by turning right despite a no-right-turn sign.

While less well known than Deliveroo or Uber, Stuart – a subsidiary of the parcels company DPD – is a leading gig economy player. It is active in more than 100 cities worldwide, most notably in the UK as a subcontractor for Just Eat in England and Wales. Just Eat declined to comment.

Sandeep Salgotra, 36, worked full-time with Stuart in Leicester until he was terminated in April because of “GPS blocking and manipulation”. Prior to his dismissal, he claims he received a number of warnings about the issue, which he did not understand, as he was unable to find any problem with his GPS connection.

When Stuart did not respond to his queries, he says, he changed his network provider. When the warnings continued, he spent £1,500 on a new phone but nothing changed. Eventually he received a response from Stuart, seen by the Observer, telling him: “You do not need to worry about being flagged at this stage … For now, everything is fine with your status.” Two weeks later, he says, he was terminated.

“It’s been really painful and I am struggling; I support my family as my wife isn’t working,” said Salgotra. “I’ve never done anything wrong in my life. I don’t understand why Stuart is treating us this way.”

Other couriers who spoke to the Observer after being terminated for routing and GPS reasons similarly described confusion over the cause of their terminations and frustration at the company’s refusal to respond to messages or engage in discussion.

One courier says he sent several emails to Stuart explaining that his phone connection sometimes dropped out in the rural area he delivered in, but did not receive a response. An appeal he submitted in February has so far gone unanswered, he says.

Another courier received a termination email citing “GPS manipulation” while in hospital recovering from a road accident that happened during the previous night’s shift. His subsequent emails, which included pictures of his written-off motorcycle, went unanswered.

Marshall said terminated couriers were “assumed without question to be acting fraudulently and denied a fair and proper process”. Many new couriers are recent migrant workers new to an area who need the GPS system and are therefore vulnerable to its faults, he points out.

The union says the GPS issues are just one of many concerns for Stuart’s couriers, some of whom are engaged in the gig economy’s longest-running strike over pay and conditions. Earlier in the strike, Stuart agreed to resolve an issue that had resulted in the unfair termination of couriers whose insurance details had been incorrectly recorded by the company.

A spokesperson for Stuart said the company “takes the issue of courier off-boarding very seriously”, adding: “We can’t comment publicly on individual cases, but we only make the decision to off-board when we have plenty of evidence to support our decision, without exceptions.”

They added: “Stuart operates an appeal process that is followed in every case where an appeal is submitted.”

For the couriers, the effects of terminations run deep. “I had to tell my kids we can’t go anywhere this year, we’re just staying in England,” said Odawa, a father of three.