Another ADR question

I have an RN2903 node with ADR enabled, reaching the gateway at:

US DR1 (SF9/BW125kHz), loraSnr: 9.5

Am I right that the SNRmargin is 12dB? (9.5dB - (-12.5dB) - 10dB) = 12dB

Yet LoraServer isn’t low*** raising the datarate below DR1. (fOpts 03 12 00 ff 01).

Do I have a setting wrong somewhere? I’ve set the min and max datarates to 0 and 3 respectively in the service profile.

Also, is there a way to tell LoraServer ADR to drop all the previous SNR readings and re-calculate the ADR settings for each node?

LoRa Server will never lower the data-rate, it will only increase it if possible.

Not sure why, but suddenly ADR is selecting from all 4 datarates, not just DR0 and DR1. That’s a good thing…

However, I’ve situated a gateway at the edge of range, and have found the gateway can hear uplinks, but the RN2903 isn’t receiving the downlinks because they are being sent at 7/500.

I can’t make sense of the RX1DROffset settings. Setting to 0 appears to only allow DR10. How do I set RX1DROffset so that column 3 is selected from LorRaWAN 1.0.2 Regional Parameters section 2.2.7 page 16, table 16?

I’ve tried 0, 3, 8 and 15 without success.