Hi,
We have using 300 tag and 100 anchors of DW3000 with stm32 in one of our project. We are TWR algorithm to calculate distance but sometime distance reduced than actual .
Everything is in stationary but still if my actual distance us 33 meter it gives 33meter and sometimes 11 meters.
Please help us for finding solution since we are in rush for delivering solution
Are you indoors in a fairly long building or tunnel?
Does this post match what you are seeing:
Look on the plus side, we didn’t see this issue until we were setting up on the day of the product launch demo. 
Yes we are using this in indoor long industrial production plant.
But after this we found this issue in smaller indoor area as well.
The first step would be to look at the CIR data and verify that the issue you are seeing is the one described in the post linked above.
If it is then there is no simple guaranteed reliable fix that I know of but ways to detect and to minimise the impact are discussed in that thread.
This has come up a number of times before, there are more threads on it if you search the board, that was simply the first I found.