Nest’s security system has been having troubles all morning. The system’s control unit — the Nest Guard — has appeared offline since around 4AM ET. While offline, homeowners haven’t been able to remotely arm or disarm the system through Nest’s app. The system continued to monitor security sensors even through the connectivity problems. However, it’s unclear if the unit was still capable of calling for help after detecting an intrusion.

More than a dozen people on Twitter said that their Guard had been disconnected in the middle of the night. The Verge’s test unit of the Nest Guard went down at 4:11AM ET as well. The Nest x Yale Lock was said to be experiencing the same problem.

Any downtime is a critical flaw for a security system

In a statement provided this afternoon, Nest said the problem impacted “a limited number” of devices and that they were now coming back online. “While these devices could not be controlled through the Nest app while offline, they were still accessible via physical interaction and continued to function,” the company wrote. The Verge’s unit remained offline immediately after receiving the statement, and Nest didn’t provide any details on what went wrong.

While it’s unclear exactly how much of the system was nonfunctional, the fact that there’s been an issue at all has some owners rightfully concerned: this is a security system, after all, which makes any amount of downtime a critical flaw.

Nest launched its home security system, Nest Secure, last September, and earlier this summer, it cut the system’s price by $100, bringing it down to $400. The system offers professional monitoring, but it’s meant for the DIY crowd who want to save money by avoiding the pricey contracts and installation fees associated with traditional alarm systems. Nest is going up against quite a few competitors — including Ring, which has an alarm system that costs half the price — and it will have to convince shoppers that its higher-tech solution is a better option than traditional and trusted tech.

This isn’t the first time Nest has seen outages of its tech, either. Back in May, the Nest Secure, Nest x Yale Lock, and even more devices experienced connectivity problems.