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A multi-system market outage affected many of the largest brokerage firm platforms early Monday, with clients taking to Twitter to voice their frustration.

The troubles came on the same day Apple enacted a 4:1 stock split and Tesla’s shares were split 5:1, and as the Dow Jones Industrial Average reconfigured three holdings. The issues were largely resolved later on Monday.

Investors using TD Ameritrade, Charles Schwab, Vanguard, Robinhood, E-Trade and other sites said they were experiencing issues in the morning.

For TD Ameritrade, some users stated on Twitter (under the hashtag #TDAmeritradedown) that weren’t able to access some mobile applications.

The brokerage’s system was down at 9:37 a.m. Eastern time, according to Downdetector, which said the number of site problems peaked at about 7,300. Most users, 76%, said they had login issues, with 15% reporting website access troubles and 7% difficulties placing trades.

(Related: Ameritrade’s Thinkorswim Outage Irks Investors)

A TD Ameritrade spokesperson said at 12:45 p.m. that issues were being addressed: “Clients are able to access their accounts and trades are being processed as usual across all TD Ameritrade platforms.”

Earlier in the day, “many clients experienced high levels of slowness on the TD Ameritrade web platforms and the TD Ameritrade mobile app,” the spokesperson added. “During this time, the thinkorswim desktop and thinkorswim mobile app were not impacted.”

Later in the afternoon Monday, TD Ameritrade said it’s issues had been  resolved. “We’re working with impacted clients to address any concerns they may have. We apologize for the inconvenience and take the performance and reliability of our trading platforms very seriously,” it said in a statement.

(TD Ameritrade is set to become part of Schwab later this year in a $26 billion deal.

Glitches at Vanguard, Schwab, Robinhood

Vanguard investors reported about 2,500 issues on Downdetector, mainly due to login problems.

The fund giant said in response to an inquiry that it “is experiencing intermittent connectivity issues impacting our websites and phones. We are working to resolve the issue as quickly as possible. We apologize for the inconvenience and thank clients for their patience.”

At about 3:30 p.m., Vanguard released a notice stating that “full access has been restored and systems are now operating as usual.” The firm recommended that clients “clear their interest cache and cookies, and recycle their web browser” before logging back onto the system.

Schwab also had troubles, with its clients voicing frustration via social media. One user tweeted: “I got stocks running and I can’t sell!! What’s going on? Both app and web are down??”

On Twitter the company stated:Due to a technical issue, Schwab.com may be intermittently inaccessible for some clients. We are working to restore service as quickly as possible. Hold times may be longer than usual. We apologize for any inconvenience.”

The number of reported issues for Schwab peaked at 1,500, according to Downdetector, while this figure was about 3,000 for Robinhood.

In addition, Robinhood, which has had system issues throughout the year, tweeted that “Some users are experiencing issues with delayed order status updates. These are display issues only, and should not impact order execution. We’ll update the status page with the latest.”

The status page said Robinhood’s systems were operational as of 1:25 p.m.

“This morning, some customers were experiencing issues with delayed order status updates. We’ve resolved the issue, and Robinhood is operational. We apologize for the inconvenience,” the firm said in a statement at 3.25 p.m.

— Check out Robinhood’s Dark Side: Irate Traders, U.S. Probe on ThinkAdvisor.