Hey,
could you discripe your problem with the calibartion process a little bit more. I trying to implemt the simple algorithmen as well. I posted some queastions as well maybe you will finde some answers here:
At the end I posted a link to a github repo where I implemended the algo from the example. Maybe you can use it for your own problem.
I can tell you my experience with the DWM3001cdk and DWM1000 dev board. Here it is normal the devices need a little bit with the exmple algorithmen to get “warm”. What I like to say is, that after a while the (1-2 minutes or a few 100 measurements) the accuracy get better and better and stablelise, not doing the other way around.
Probibly there is a mistake with your delays (waiting for response time or delayed sending time) or you facing more and more side effects like multipath. I think you should have a look at the diagnostics of your data. You can a finde a example Code provided by Qorovo ex_02c_rx_diagnostics (https://www.qorvo.com/products/p/DWM3001CDK#documents and than under software) or a discrption in the DW3000 API Guide.