DATARATE:850K,PRF:16M Unable to communicate

Hello,My rate is 850k, PRF is 16m, data cannot be received;
But when I change PRF to 64M, if all other configurations are unchanged, I can receive data. What’s the reason?
Here are my two configurations:
{
2, /* Channel number. /
DWT_PRF_64M, /
Pulse repetition frequency. /
DWT_PLEN_1024, /
Preamble length. Used in TX only. /
DWT_PAC16, /
Preamble acquisition chunk size. Used in RX only. /
3, /
TX preamble code. Used in TX only. /
3, /
RX preamble code. Used in RX only. /
0, /
0 to use standard SFD, 1 to use non-standard SFD. /
DWT_BR_850K, /
Data rate. /
DWT_PHRMODE_STD, /
PHY header mode. /
(1024 + 1 + 8 - 16) /
SFD timeout (preamble length + 1 + SFD length - PAC size). Used in RX only. */
}normal

{
2, /* Channel number. /
DWT_PRF_16M, /
Pulse repetition frequency. /
DWT_PLEN_1024, /
Preamble length. Used in TX only. /
DWT_PAC16, /
Preamble acquisition chunk size. Used in RX only. /
3, /
TX preamble code. Used in TX only. /
3, /
RX preamble code. Used in RX only. /
0, /
0 to use standard SFD, 1 to use non-standard SFD. /
DWT_BR_850K, /
Data rate. /
DWT_PHRMODE_STD, /
PHY header mode. /
(1024 + 1 + 8 - 16) /
SFD timeout (preamble length + 1 + SFD length - PAC size). Used in RX only. */
}abnormal

I Don’t know the reason, but i can tell you that we also experimented with the PRF=16MHZ for TDoA applications using the TTK1000 Kit and the communication is not reliable, what I mean:

With PRF=64MHz everything works as is expected
With PRF=16MHz we see big latency most of the time is not possible to locate a tag, 80% of the time we don’t get any good position (X:NaN, Y:Nan, only outliers or jumps)

I don’t know exactly why, but I learned that we should choose 64MHz always to deploy a project.