SX1262 Lorawan Downlink Range Issues

I have developed and am testing a long range lorawan class A node (v1.0.3 US915) using the SX1262 chipset in a Fanstel LR62E module.

I have gateways which are able to pick up many of the transmissions around -10db SNR and between -100 to -120dBm RSSI. I am transmitting at maximum chipset power of +22dBm at about DR1-DR3. DR0 appears to be unreceived by the gateways. The link does not drop any packets to the gateway and the gateways are able to process all uplinks from the node.

During device downlinks such as a join-accept or a confirmed-down message, the node is not able to receive the downlinks from the gateway transmitting at +28dBm at data rates between DR9-DR13 (BW500khz, SF8-11). The chipset operates in RX-boosted mode for maximum sensitivity. The environment is not challenging with trees and range being the largest interferer.

Downlinks work well while the node is closer to the gateway (i.e. anything with a >=0 SNR) but as the range increases, it begins dropping more packets until no downlinks are received. After the join-accept message, the device operates with a DR offset of 2 which sets the downlink bitrate to be the same as the uplink bitrate. This marginally improves the reception rate, but not enough to mirror the same range as the uplinks. The join-accept downlinks do not appear to transmit with any DR offset and are increasingly difficult to receive. The gateway is confirmed to be sending all downlinks (through TTN and through SDR scans) so it is not a gateway issue.

I am hoping to find if there are possible solutions to improve the downlink range of the device. I would appreciate any advice on the topic.