Sudden spikes in distance measured?

Hi, I’m using the Single Side Two way ranging scheme. From time to time, and this is in no way persistent, a value considerably larger than normal will be measured.

For example for a distance of 2 meters, sometimes the result would be 2.8 meter. It happens randomly and rarely.

Anything worth being alarmed about on this? And if so how do I decrease the chance of its happening?