Grimes' Coachella performance didn't go as planned ... plagued by constant stoppages she blamed on technical difficulties -- before she let off several frustrated shrieks.

The singer-songwriter took the stage on Saturday night out in Indio, CA, presumably ready to bring the house down ... though ultimately she couldn't keep the music up.

Check out the clip ... Grmies' show on the Sahara Stage is moving along just fine before an incorrectly timed transition throws the musician into a bit of a tailspin.

She tells the audience it's hard to explain what exactly's happening, but she basically says her show's having a major technical issue ... before adding she can't fix a tempo problem because she isn't great at math.

It's a little bizarre ... but, basically, it sounds like the transitions are coming too fast for her to predict -- causing changes she's just not expecting.

Ultimately, the concert goes on for a little while longer ... until something major sets Grimes off and she chucks down her headphones in disgust. She no longer tries to explain the issue but simply belts off a few anguished cries.

It's a sad -- somewhat awkward -- moment, and you can't help but feel for Grimes here ... 'cause she obviously wanted to put on a great show for her fans.