I have a stray Elephant's Bush that grew from an online order lime tree. But it has yellow flowers, not red. Could it be something else? The stems are more red than brown.
This is, definitely, Portulaca oleracea. Common Purslane. Not Portulacaria. They have a similar looking name, but they are different.
https://www.gardeningknowhow.com/plant-problems/weeds/purslane-control.htm