I'm having a strange problem after customers complete checkout in Magento 2.2. About 15-20% of the time when they click "Place Order," the order is placed on the backend and they see the "You have no items in your shopping cart" page on the frontend. However, the majority of the time it does take them to the checkout success page as it should.
I'm pulling my hair out trying to figure out how it's skipping the checkout success page from time to time. I've tried to eliminate other variables by disabling plugins, payment methods, etc., but it's completely random. Anyway, I though that if I were in Developer mode and had the debugging log enabled, I'd see some clues when it does skip the checkout success page. No luck. The debug log is being written, but it doesn't log anything different from when the checkout success is being skipped and when it isn't.
Anyway, I need some input as to the best way to troubleshoot and debug this strange problem. What is everyone's preferred method to debugging in Magento 2? Any online resources that would help me understand the debug process better? Thanks!