Simple, a Portland-based digital banking service, experienced a glitch over the weekend that left around 5 percent of their customers unable to view transactions or an accurate balance in their accounts.

Simple spokeswoman Amy Dunn says an engineering team resolved the issue earlier this morning. But the event raises questions for a company that only offers customers access to their bank accounts digitally.

Simple is a branchless bank—your phone is your transaction hub. It pieces together all the innovations of other mobile money services, like check deposit via smartphone photo and mobile transfers to other users, with typical banking features like a physical debit card and a network of ATMs.

The platform is one that also allows customers to budget and set spending goals, tasks that become more difficult if transactions are hidden.

Market Watch first reported on the glitch yesterday. Reporter Kari Paul is a Simple user whose banking capability was affected. Exactly how many other users had issues with Simple over the weekend is unclear, as the company does not report its total number of customers.

"I love the digital bank, with its clean design and great user experience," Paul wrote in the article. "But for three days, I have not been able to access my account's accurate balance or recent activity."

For disenchanted customers, like Paul, this weekend's functionality issue led to banking regrets.

"In November, I ditched Wells Fargo for Simple," she wrote, "and I haven't looked back. Until now."

Dunn says that the issue was the result of maintenance on a back-end service, something that happens often for tech companies and that engineering teams work quickly to resolve.

Large banks, as Dunn points out, don't have to account for technology issues like a mobile-only company does. That doesn't mean problems don't arise. Bank of America experienced an entire week of website disruptions in 2011, which led to some customers being reimbursed for lost money, Market Watch reported.

Bugs and glitches are an inevitable product of technologically based services. But Dunn says Simple works quickly resolve tech problems and provides access to customer support services.

"Large banks are less visible," Dunn says. "As a tech company the reason we exist is clarity."