Thank you for the ideas. I do not use asynchronous processes, the GPIO ISR does nothing just sets a static volatile boolean variable. The power is also o.k.
Finally I’ve tried a workaround that solved this problem seemingly (multiple devices work for more than a day continuously doing TWR in every 3 seconds). Before re-enabling Rx after Tx (even after delayed Tx fail) I execute a TRXOFF command and a receiver-only soft reset.
PS: the Decawave team does not read this forum? 
These problems are related to undocumented chip internals, but the chip designers there surely know every little thing about them. Just not bother with these questions…